chore: add empty root-level Program.cs placeholder

- Add DocumentService.Tests.Live (xUnit live tests, GUID CC5A7D7B) to solution
  under the existing Tests solution folder
- Add DocumentService.Tests.NuGet (smoke-test console app, GUID EE3E7C50) to
  solution under the Tests solution folder
- Expand GlobalSection(SolutionConfigurationPlatforms) to include x64 and x86
  variants for Debug and Release alongside the existing Any CPU entries
- Add corresponding ProjectConfigurationPlatforms entries for all projects
  (existing + new) so VS/MSBuild can resolve the correct output paths when
  targeting x64/x86 explicitly

AGENTS.md

@@ -0,0 +1,726 @@
+# AGENTS.md
+
+Agent guidance for DocumentService service. Read this before working on the codebase.
+
+---
+
+## ⚠️ CRITICAL: Architecture Decision Change
+
+**Previous developer used Minimal API** (`DocumentEndpoints.cs`), but this is **WRONG**.
+
+**YOU MUST use Controller-based approach** as specified in `CONTROLLER_ENDPOINTS.md`.
+
+### Key Differences
+
+| Previous Approach (WRONG) | Required Approach (CORRECT) |
+|---------------------------|------------------------------|
+| Minimal API (`DocumentEndpoints.cs`) | **Controllers** (`PdfValidationController`, etc.) |
+| Only Base64 JSON | **Both multipart/form-data AND Base64 JSON** |
+| `/api/v1/documents/validate` | **`/api/pdf/validation/validate`** |
+
+**Do NOT follow ROADMAP.md's "Minimal API" guidance.** It conflicts with the requirements.
+
+### Migration Required
+
+**Existing code that needs replacement:**
+- `DocumentService.API/Endpoints/v1/DocumentEndpoints.cs` → Delete, replace with Controllers
+- `Program.cs` line 72: `app.MapDocumentEndpoints()` → Replace with `app.MapControllers()`
+- `Program.cs` line 44: Add `builder.Services.AddControllers()`
+- All DTOs → Support **BOTH** `IFormFile` (multipart) AND `Base64String` (JSON)
+
+**Dual Input Support Required:**
+- Controllers must accept **BOTH** file upload (multipart/form-data) and Base64 JSON
+- Each endpoint should have overloads or flexible parameter binding
+- Preserve existing Base64 functionality while adding file upload support
+
+---
+
+## Architecture & Development Approach
+
+**Clean Architecture with Controller-Based API:**
+- 4 layers: API → Application → Infrastructure → Domain
+- Domain has **ZERO** external dependencies (only standard .NET)
+- Feature-driven development: complete one feature end-to-end before starting the next
+- Feature = Domain + Infrastructure + Application + **Controller** + Tests + Swagger (all layers)
+
+**Dependency flow (enforced):**
+```
+API → Application → Domain
+API → Infrastructure → Application
+Infrastructure → Application (for interfaces only)
+Domain → NOTHING
+```
+
+**Vertical Slice structure** (NOT horizontal layers):
+```
+Features/Documents/
+├── ValidatePdf/
+│   ├── ValidatePdfQuery.cs          (request)
+│   ├── ValidatePdfHandler.cs        (logic)
+│   └── ValidatePdfValidator.cs      (validation)
+└── ExtractSwissQrCode/
+    ├── ExtractSwissQrCodeQuery.cs
+    ├── ExtractSwissQrCodeHandler.cs
+    └── ExtractSwissQrCodeValidator.cs
+```
+
+All files for a feature live together. Do NOT create separate Commands/, Handlers/, Validators/ folders.
+
+---
+
+## 🏗️ Architecture Principles
+
+### Clean Architecture (Pragmatic)
+
+**4 Layers with strict dependency rules:**
+- API → Application → Domain
+- Infrastructure → Application (interfaces only)
+- Domain → NOTHING (zero external dependencies)
+
+**Key Principles:**
+- ✅ Testability (Application layer mocks Infrastructure services)
+- ✅ Replaceability (swap DevExpress without touching Application)
+- ✅ Separation of Concerns
+- ❌ NO overengineering (only what we need, YAGNI principle)
+- ❌ NO speculative abstractions (wait for 2nd use case)
+
+### CQRS with MediatR
+
+**Why MediatR:**
+- 1 Command/Query = 1 Handler = 1 Responsibility
+- Isolated, testable handlers
+- Pipeline Behaviors (Validation, Logging) run centrally
+- Avoids bloated services with 20+ methods
+
+**Pattern:**
+- **Command:** Modifies data (ApplyStamp, EmbedCertificate)
+- **Query:** Reads data (ValidatePdf returns metadata only)
+
+**Pipeline:** ValidationBehavior → LoggingBehavior → Handler
+
+### Vertical Slice Architecture
+
+**NOT Horizontal** (Commands/, Handlers/, Validators/ folders)  
+**YES Vertical** (all files for one feature together)
+
+**Benefits:**
+- Related code stays together (high cohesion)
+- Easier to find ("Where's ValidatePdf?" → one folder!)
+- Easier to modify (all files in same folder)
+- Fewer merge conflicts in teams
+
+### Exception-Based Error Handling
+
+**NO Result<T> pattern library**
+
+**Flow:**
+1. FluentValidation (DTO level) → ValidationException → 400
+2. Domain validation → DomainValidationException → 400
+3. Business logic → DomainException → 400/404
+4. Infrastructure → PdfProcessingException → 500
+
+**Middleware:** Central exception handler maps exceptions to HTTP status codes
+
+**Why exceptions:**
+- Simpler code (no `if (result.IsSuccess)` everywhere)
+- Less boilerplate (no Result<T> wrapping)
+- Standard .NET exception flow
+- Centralized error handling (one place to maintain)
+
+### Feature-Driven Development
+
+**Feature-Driven (NOT Layer-by-Layer):**
+- Complete one feature end-to-end before starting next
+- Feature = Domain + Infrastructure + Application + API + Tests + Swagger
+- Feature is DONE when testable in Swagger UI
+
+**Why:**
+- Faster value delivery (Feature 1 done in ~1 day)
+- Clear definition of done (Swagger testable)
+- Less complexity (not all layers in parallel)
+- Better learning (pattern repeats)
+
+**Alternative rejected:** Complete all Domain → all Infrastructure → all Application → all API  
+**Problem:** Too much speculative code without visible results
+
+### Test-Driven Development (TDD)
+
+**Flow:** Red → Green → Refactor
+
+**Test Pyramid:**
+- **Unit Tests (many):** Value Objects, Handlers, Services
+- **Integration Tests (some):** Endpoints, MediatR Pipeline
+- **E2E Tests (few/none):** API is already top-level
+
+**Why TDD:**
+- Tests as documentation
+- Tests as safety net for refactoring
+- Better design (testable = good code)
+- No forgotten tests (test comes FIRST)
+
+### Cross-Cutting Concerns Timing
+
+**Multi-Tenancy Implementation Deferred**
+
+**Decision:** Implement multi-tenancy (X-API-Key header, tenant database, Redis cache) AFTER all synchronous PDF operation features are complete.
+
+**Why:**
+- Multi-tenancy affects ALL endpoints
+- Better to implement once for all features (avoid repetition)
+- Easier to test features first without tenancy, then add tenancy layer
+- Cleaner separation: Features first, then cross-cutting concerns
+
+**Impact on current architecture:**
+- ❌ NO Entity Framework yet (tenant database comes with multi-tenancy)
+- ❌ NO Redis yet (API key caching comes with multi-tenancy)
+- ❌ NO X-API-Key authentication yet (comes with multi-tenancy)
+- ✅ All features currently work without authentication
+
+**When to implement:**
+After completing all Phase 1-3 controllers (PdfValidation, PdfAttachment, SwissQrCode, PdfOperations, PdfConversion), then add multi-tenancy to ALL endpoints in one refactoring phase.
+
+---
+
+## Build, Test, Run
+
+**Build:**
+```powershell
+dotnet build
+```
+
+**Run tests (101 passed, 7 skipped as of Feature 7 - PDF Stamp):**
+```powershell
+dotnet test
+```
+
+**Run API (Development):**
+```powershell
+dotnet run --project DocumentService.API
+```
+Swagger UI: `https://localhost:7186/swagger`  
+Serilog UI: `https://localhost:7186/serilog-ui` (Web-based log viewer)
+
+**Target framework:** .NET 8.0  
+**SDK required:** 8.0.412 or later (repo has 8.0.412–10.0.203 available)
+
+---
+
+## Key Libraries & Their Roles
+
+| Library | Purpose | Where Used |
+|---------|---------|------------|
+| **DevExpress.Document.Processor** (26.1.3) | PDF operations (validation, QR extraction, attachments) | Infrastructure layer only |
+| **Codecrete.SwissQRBill.Generator** (3.4.0) | Swiss QR Bill parsing (Standard 2.0) | Infrastructure.Services.QrCodeProcessing |
+| **ZXing.Net.Bindings.Windows.Compatibility** (0.16.14) | QR code image decoding | Infrastructure.Services.QrCodeProcessing |
+| **MediatR** (14.1.0) | CQRS: 1 handler per feature | Application layer |
+| **FluentValidation** (12.1.1) | Request validation (runs via ValidationBehavior before handlers) | Application layer |
+| **Serilog.AspNetCore** (10.0.0) | Structured logging | API layer |
+| **Serilog.Sinks.SQLite** (7.0.0) | SQLite log persistence | API layer |
+| **Serilog.UI** (3.2.0) + **Serilog.UI.SqliteProvider** (1.1.0) | Web-based log viewer UI | API layer |
+
+**Critical:** DevExpress requires a license. All PDF operations use `DevExpress.Pdf.PdfDocumentProcessor`.
+
+---
+
+## Exception Handling Strategy
+
+**No Result<T> pattern.** Use exceptions + central middleware.
+
+**Flow:**
+1. FluentValidation validates request DTOs → throws `ValidationException` → HTTP 400
+2. Domain validation in Value Objects → throws `DomainValidationException` → HTTP 400
+3. Business logic errors → throws `DomainException` subtypes → HTTP 400/404/500
+4. Infrastructure errors (e.g., PDF parsing) → throws `PdfProcessingException` → HTTP 500
+
+**Middleware maps exceptions to HTTP status codes** (`ExceptionHandlingMiddleware.cs`).
+
+Do NOT add `if (result.IsSuccess)` checks. Throw exceptions for errors. The middleware handles the rest.
+
+---
+
+## Required Controllers & Endpoints
+
+**See `CONTROLLER_ENDPOINTS.md` for complete specification.**
+
+### Priority Order
+
+**Phase 1 (PRIORITY):**
+1. `PdfValidationController` – 2 endpoints
+   - `POST /api/pdf/validation/validate` (Basic PDF validation)
+   - `POST /api/pdf/validation/validate-pdfa` (PDF/A conformance)
+2. `PdfAttachmentController` – check endpoint
+   - `POST /api/pdf/attachments/check` (Attachment detection)
+3. `SwissQrCodeController` – extract endpoint
+   - `POST /api/swissqrcode/extract` (Swiss QR Bill extraction)
+4. `PdfAttachmentController` – extract endpoint
+   - `POST /api/pdf/attachments/extract` (Extract attachments as ZIP)
+5. `PdfOperationsController` – merge endpoint
+   - `POST /api/pdf/operations/merge` (Merge multiple PDFs)
+
+**Phase 2:**
+6. `PdfOperationsController` – stamp & annotate
+   - `POST /api/pdf/operations/stamp` (Add stamps)
+   - `POST /api/pdf/operations/annotate` (Add annotations)
+7. `PdfAttachmentController` – add attachment
+   - `POST /api/pdf/attachments/add` (Embed attachments in PDF/A-3)
+
+**Phase 3:**
+8. `PdfConversionController` – PDF ↔ PDF/A conversion
+   - `POST /api/pdf/conversion/to-pdfa` (Convert to PDF/A)
+   - `POST /api/pdf/conversion/from-pdfa` (Convert from PDF/A)
+
+**Removed:**
+- `PdfRenderController` – Moved to .NET client library (WinForms/WPF DevExpress controls)
+
+### Current Status
+
+| Controller | Status | Tests |
+|-----------|--------|-------|
+| **PdfValidationController** | ✅ DONE | 13 (7 validate + 6 validate-pdfa) |
+| **SwissQrCodeController** | ✅ DONE | 2 |
+| **PdfAttachmentController** | ⏳ Partial (2/3 endpoints) | 10 (4 check + 6 extract) |
+| **PdfOperationsController** | ⏳ Partial (3/3 endpoints, integration tests pending) | 29 (7 merge + 22 annotate: 12 unit + 10 integration) |
+| **PdfConversionController** | ⏳ Pending | 0 |
+
+**PdfAttachmentController Status:**
+- ✅ `POST /api/pdf/attachments/check` - DONE (with multipart + Base64 support)
+- ✅ `POST /api/pdf/attachments/extract` - DONE (Phase 1, Priority 4) - Returns ZIP with all attachments
+- ⏳ `POST /api/pdf/attachments/add` - TODO (Phase 2, Priority 7)
+
+**PdfOperationsController Status:**
+- ✅ `POST /api/pdf/operations/merge` - DONE (Phase 1, Priority 5) - Merges multiple PDFs with optional page ranges (multipart + Base64)
+- ✅ `POST /api/pdf/operations/annotate` - DONE (Phase 2, Priority 6) - Adds annotations (TextMarkup/FreeText/StickyNote/Circle/Square) with multipart + Base64 support
+- ✅ `POST /api/pdf/operations/stamp` - DONE (Phase 2, Priority 6) - Adds text/image/predefined stamps (multipart + Base64 support, origin/rotation/opacity/placement)
+
+**Note:** PdfRenderController removed - moved to .NET client library.
+
+---
+
+## Adding a New Feature
+
+**Required steps (follow CONTROLLER_ENDPOINTS.md):**
+
+1. **Domain:** Value Objects, Exceptions (if needed)
+2. **Infrastructure:** Service interface + DevExpress implementation + unit tests
+3. **Application:** Query/Command + Handler + FluentValidator + DTOs + unit tests
+4. **API:** **Controller** + actions + integration tests
+5. **Swagger:** XML comments on controller actions + DTOs
+
+**Example (PdfValidationController):**
+```
+Step 1: Application/Features/Documents/ValidatePdf/
+  - ValidatePdfCommand.cs (record)
+  - ValidatePdfHandler.cs (IRequestHandler)
+  - ValidatePdfValidator.cs (AbstractValidator)
+Step 2: API/Controllers/PdfValidationController.cs
+  - [HttpPost("validate")] action
+  - Accepts IFormFile (multipart/form-data)
+  - Returns ValidatePdfResponse
+Step 3: XML comments + [ProducesResponseType] attributes
+```
+
+**CRITICAL: Support BOTH multipart/form-data AND Base64 JSON for all file-based endpoints.**
+
+**Input Flexibility:**
+- Primary: `IFormFile` (multipart/form-data) - for direct file uploads
+- Secondary: `Base64String` (application/json) - for API clients that can't send multipart
+
+Do NOT skip steps. Each feature is done when it's **testable in Swagger UI with both input methods**.
+
+---
+
+## Test Data
+
+**Embedded test PDFs:**
+- `TestData/Pdfs/valid.pdf` (simple PDF for validation)
+- `TestData/Pdfs/pdfWithSwissQRCode.pdf` (Swiss QR Code on last page)
+- `TestData/Pdfs/pdfWithMoreThanOneAttachment.pdf` (6 attachments)
+
+**All test PDFs are EmbeddedResource.** Access via:
+```csharp
+var stream = Assembly.GetExecutingAssembly()
+    .GetManifestResourceStream("DocumentService.Tests.TestData.Pdfs.valid.pdf");
+```
+
+**Do NOT commit new binary files** without marking them as `<EmbeddedResource>`.
+
+---
+
+## Test Structure & Strategy
+
+**3-folder structure (CORRECT approach by previous developer):**
+
+```
+DocumentService.Tests/
+├── Integration/
+│   └── API/
+│       ├── PdfValidationControllerTests.cs (13 tests)
+│       └── ExtractSwissQrCodeEndpointTests.cs (2 tests)
+├── TestData/
+│   └── Pdfs/ (EmbeddedResource PDFs)
+├── Unit/
+│   ├── Application/
+│   │   └── Features/
+│   │       ├── ValidatePdf/
+│   │       │   └── ValidatePdfHandlerTests.cs (2 tests)
+│   │       ├── ValidatePdfA/
+│   │       │   └── ValidatePdfAQueryHandlerTests.cs (4 tests)
+│   │       └── ExtractSwissQrCode/
+│   │           └── ExtractSwissQrCodeHandlerTests.cs (2 tests)
+│   └── Infrastructure/
+│       └── Services/
+│           └── PdfProcessing/
+│               └── DevExpressPdfProcessorTests.cs (7 tests)
+```
+
+**✅ Why this structure is CORRECT:**
+
+1. **Integration vs Unit separation:**
+   - **Integration:** WebApplicationFactory → REAL API calls (HTTP, middleware, MediatR pipeline, DevExpress)
+   - **Unit:** Mock-based ISOLATED tests (Handler only depends on mocked IPdfProcessor)
+
+2. **TestData centralization:**
+   - All 3 layers share same EmbeddedResource PDFs (no duplication)
+   - Accessed via `Assembly.GetManifestResourceStream()`
+
+3. **Vertical Slice compliance:**
+   - `Unit/Application/Features/ValidatePdf/` → Each feature's tests co-located
+   - Matches Application layer structure exactly
+
+4. **Test Pyramid:**
+   - **Unit tests (60+):** Fast, isolated, many scenarios
+   - **Integration tests (27):** Slower, full pipeline, critical paths only
+
+**Test count:** 101 passed, 7 skipped (as of Feature 6 - PDF Annotation)
+
+**Test breakdown by feature:**
+- Feature 1 (PDF Validation): 13 integration tests
+- Feature 2 (Swiss QR Code): 2 integration tests  
+- Feature 3 (PDF/A Validation): 6 integration tests (validate-pdfa) + 4 unit tests (handler)
+- Feature 4 (PDF Attachments): 10 tests (4 check + 6 extract integration)
+- Feature 5 (PDF Merge): 7 integration + 10 unit tests (DevExpressPdfProcessor)
+- Feature 6 (PDF Annotation): 10 integration + 12 unit tests (DevExpressPdfProcessor)
+- Infrastructure: 37 unit tests (DevExpressPdfProcessor for validation, attachments, merge, annotation)
+
+**FluentValidation in tests:**
+- Base64 format validation happens in `ValidatePdfQueryValidator` and `ValidatePdfAQueryValidator`
+- Prevents `FormatException` from reaching handler (caught as 400 Bad Request, not 500)
+- Unit tests verify handler behavior with valid inputs only
+- Integration tests verify full validation pipeline (including FluentValidation)
+
+---
+
+## Swiss QR Code Feature (Feature 2)
+
+**Swiss QR Bill Standard 2.0** requires:
+- QR code is on the **last page** of the PDF (not first!)
+- Use `DevExpress.Pdf.PdfDocumentProcessor` to render last page as image
+- Use `ZXing` to decode QR code from image
+- Use `Codecrete.SwissQRBill.Generator` to parse Swiss QR Bill payload
+
+**Known quirks:**
+- PDF must be rendered at **300 DPI** for reliable QR detection
+- Alternative procedure parameters (AV1, AV2) are split by newline, not semicolon
+
+---
+
+## MediatR Pipeline Behaviors
+
+**Two behaviors run for EVERY request:**
+
+1. **ValidationBehavior** (runs first): Executes all `IValidator<TRequest>` and throws `ValidationException` if invalid
+2. **LoggingBehavior** (runs second): Logs request name + execution time
+
+**Registered in:** `Application/DependencyInjection.cs`
+
+Do NOT manually call validators in handlers. The pipeline does it.
+
+---
+
+## Controller Pattern (CORRECT Approach)
+
+**Controllers must support BOTH file upload and Base64 input.**
+
+### Option 1: Separate Endpoints (Recommended)
+
+```csharp
+[ApiController]
+[Route("api/pdf/validation")]
+public class PdfValidationController : ControllerBase
+{
+    private readonly IMediator _mediator;
+
+    public PdfValidationController(IMediator mediator)
+    {
+        _mediator = mediator;
+    }
+
+    /// <summary>
+    /// Validates a PDF document (multipart/form-data)
+    /// </summary>
+    [HttpPost("validate")]
+    [Consumes("multipart/form-data")]
+    [ProducesResponseType(typeof(ValidatePdfResponse), 200)]
+    [ProducesResponseType(typeof(ProblemDetails), 400)]
+    public async Task<IActionResult> ValidateFromFile(IFormFile file, CancellationToken ct)
+    {
+        using var ms = new MemoryStream();
+        await file.CopyToAsync(ms, ct);
+        byte[] pdfBytes = ms.ToArray();
+
+        var command = new ValidatePdfCommand(pdfBytes);
+        var result = await _mediator.Send(command, ct);
+        
+        return Ok(result);
+    }
+
+    /// <summary>
+    /// Validates a PDF document (Base64 JSON)
+    /// </summary>
+    [HttpPost("validate")]
+    [Consumes("application/json")]
+    [ProducesResponseType(typeof(ValidatePdfResponse), 200)]
+    [ProducesResponseType(typeof(ProblemDetails), 400)]
+    public async Task<IActionResult> ValidateFromBase64(
+        [FromBody] ValidatePdfRequest request, 
+        CancellationToken ct)
+    {
+        var query = new ValidatePdfQuery(Base64String.Create(request.Base64Pdf));
+        var result = await _mediator.Send(query, ct);
+        
+        return Ok(result);
+    }
+}
+```
+
+### Option 2: Single Endpoint with Model Binding
+
+```csharp
+public class PdfInputModel
+{
+    public IFormFile? File { get; set; }
+    public string? Base64Pdf { get; set; }
+}
+
+[HttpPost("validate")]
+public async Task<IActionResult> Validate([FromForm] PdfInputModel input, CancellationToken ct)
+{
+    byte[] pdfBytes = input.File != null 
+        ? await GetBytesFromFile(input.File)
+        : Base64String.Create(input.Base64Pdf!).ToByteArray();
+    
+    // Process...
+}
+```
+
+**Use Controllers, NOT Minimal API endpoints.**
+
+---
+
+## Configuration
+
+**appsettings.json sections:**
+- `DocumentServiceSettings` (future: file size limits, temp paths)
+- `RedisSettings` (future: multi-tenancy caching)
+- `ApiKeySettings` (future: authentication)
+
+**Currently:** All features work without authentication. Multi-tenancy is deferred until after all sync features are complete.
+
+---
+
+## Coding Standards
+
+### Primary Constructors
+**ALWAYS use primary constructors** (C# 12 feature) unless there's a technical limitation.
+
+**✅ Correct:**
+```csharp
+public class PdfValidationController(IMediator mediator, ILogger<PdfValidationController> logger) : ControllerBase
+{
+    // Use parameters directly, no field declarations needed
+    public async Task<IActionResult> Validate(...)
+    {
+        await mediator.Send(...);
+    }
+}
+```
+
+**❌ Wrong:**
+```csharp
+public class PdfValidationController : ControllerBase
+{
+    private readonly IMediator _mediator;
+    private readonly ILogger<PdfValidationController> _logger;
+    
+    public PdfValidationController(IMediator mediator, ILogger<PdfValidationController> logger)
+    {
+        _mediator = mediator;
+        _logger = logger;
+    }
+}
+```
+
+### Controller Responsibilities
+**Controllers should be thin.** Do NOT add mapping logic.
+
+**✅ Correct:**
+```csharp
+public async Task<IActionResult> Validate([FromBody] ValidatePdfRequest request, CancellationToken ct)
+{
+    // Direct pass-through to MediatR
+    var result = await mediator.Send(request, ct);
+    return Ok(result);
+}
+```
+
+**❌ Wrong:**
+```csharp
+public async Task<IActionResult> Validate([FromBody] ValidatePdfRequest request, CancellationToken ct)
+{
+    // Manual mapping (WRONG!)
+    var command = new ValidatePdfCommand(request.Base64Pdf);
+    var metadata = await mediator.Send(command, ct);
+    var response = new ValidatePdfResponse(metadata.PageCount, ...);
+    return Ok(response);
+}
+```
+
+**If mapping is absolutely necessary:** Use AutoMapper.
+
+### Request DTOs - Flexible Input
+**Support BOTH `byte[]` and `Base64String` in requests.**
+
+```csharp
+public record ValidatePdfRequest
+{
+    public byte[]? PdfBytes { get; init; }
+    public string? Base64Pdf { get; init; }
+}
+```
+
+**FluentValidation:** Ensure exactly ONE is provided:
+```csharp
+public class ValidatePdfRequestValidator : AbstractValidator<ValidatePdfRequest>
+{
+    public ValidatePdfRequestValidator()
+    {
+        RuleFor(x => x)
+            .Must(x => (x.PdfBytes != null && x.PdfBytes.Length > 0) ^ 
+                       (!string.IsNullOrWhiteSpace(x.Base64Pdf)))
+            .WithMessage("Either PdfBytes or Base64Pdf must be provided, but not both");
+    }
+}
+```
+
+**Handler:** Use `byte[]` if available, otherwise convert Base64:
+```csharp
+public async Task<PdfMetadata> Handle(ValidatePdfRequest request, CancellationToken ct)
+{
+    byte[] pdfBytes = request.PdfBytes ?? Convert.FromBase64String(request.Base64Pdf!);
+    return await _processor.ValidateAsync(pdfBytes);
+}
+```
+
+### No Unnecessary Value Objects
+**Do NOT create value objects for simple types** (e.g., Base64String).
+
+**❌ Wrong:** Creating `Base64String` value object just to wrap `string`
+**✅ Correct:** Use `string` directly + extension methods if needed
+
+**Why:** 
+- Performance overhead (validation runs twice: once in value object, once in FluentValidation)
+- Unnecessary abstraction (YAGNI principle)
+- `Convert.FromBase64String()` already validates format
+
+### Exception Handling in Controllers
+**Let FormatException bubble up naturally.** ExceptionHandlingMiddleware will catch it.
+
+```csharp
+// Handler
+byte[] pdfBytes = request.PdfBytes ?? Convert.FromBase64String(request.Base64Pdf!);
+// If Base64 is invalid, FormatException → Middleware → 400 Bad Request
+```
+
+**Middleware handles:**
+- `FormatException` → 400 Bad Request
+- `ValidationException` → 400 Bad Request
+- `DomainException` → 400/404
+- `PdfProcessingException` → 500
+
+---
+
+## Git Commit Guidelines
+
+### ⚠️ CRITICAL: Never Commit Without Approval
+**NEVER run `git commit` without explicit user approval.**
+
+### Systematic Commits
+**Do NOT commit everything in one giant commit.**
+
+**✅ Correct approach:**
+1. Complete one logical change (e.g., "Add PdfValidationController")
+2. Stage only related files: `git add <specific-files>`
+3. Ask user: "Ready to commit 'Add PdfValidationController'?"
+4. After approval: `git commit -m "Add PdfValidationController with dual input support"`
+5. Repeat for next logical change
+
+**❌ Wrong approach:**
+```bash
+git add -A
+git commit -m "Migrate everything to controllers, update tests, add AGENTS.md, delete ROADMAP.md"
+# This is TOO MUCH in one commit!
+```
+
+**Good commit messages:**
+- `feat: Add PdfValidationController with multipart/form-data support`
+- `refactor: Replace Base64String value object with direct string usage`
+- `test: Add integration tests for PdfValidationController`
+- `docs: Add AGENTS.md with architecture guidance`
+- `chore: Delete deprecated ROADMAP.md`
+
+**Commit size guideline:** 1-5 files per commit, one logical change
+
+---
+
+## What NOT to Do
+
+- ❌ Do NOT create horizontal folders (Commands/, Handlers/, Validators/)
+- ❌ Do NOT add Entity Framework until multi-tenancy phase
+- ❌ Do NOT use Minimal API endpoints (use Controllers instead)
+- ❌ Do NOT support only ONE input type (must support BOTH multipart AND Base64)
+- ❌ Do NOT use Result<T> pattern (use exceptions)
+- ❌ Do NOT skip tests (TDD: write test first, then implementation)
+- ❌ Do NOT add dependencies to Domain layer (keep it clean!)
+- ❌ Do NOT commit without user approval
+- ❌ Do NOT use old-style constructors (use primary constructors)
+- ❌ Do NOT add mapping logic in controllers (keep them thin)
+- ❌ Do NOT create unnecessary value objects (YAGNI principle)
+
+---
+
+## Debugging Tips
+
+**DevExpress PDF errors:**
+- Check if file is actually a valid PDF (magic bytes: `%PDF-`)
+- DevExpress throws generic exceptions; wrap in try-catch and add context
+
+**Swiss QR Code not found:**
+- Verify QR is on **last page** (not first)
+- Check DPI setting (300 DPI required, see ROADMAP.md Feature 2)
+- Use `ZXing` with `TryHarder` hint enabled
+
+**Attachment count wrong:**
+- Search entire PDF stream, not just first 1000 chars (see ROADMAP.md fix log 17.01.2025)
+- Count `/EmbeddedFiles` object references correctly (not divided by 2)
+
+---
+
+## References
+
+- **CONTROLLER_ENDPOINTS.md** – **PRIMARY SOURCE** for API specification (all planned endpoints)
+- **REQUIRED_FEATURES.md** – Business requirements (what PDF operations are needed and why)
+- **ROADMAP.md** – Feature-by-feature implementation plan (1101 lines, detailed) **NOTE: Uses Minimal API, which is incorrect. Follow CONTROLLER_ENDPOINTS.md instead.**
+- **DevExpress Docs** – https://docs.devexpress.com/OfficeFileAPI/
+- **Swiss QR Bill Standard** – https://www.ferd-net.de/ (ZUGFeRD/XRechnung context)
+
+**When implementing endpoints:** Follow CONTROLLER_ENDPOINTS.md, NOT ROADMAP.md's Minimal API approach.

CONTROLLER_ENDPOINTS.md

@@ -0,0 +1,352 @@
+# DocumentService - Controller & Endpoint Specification
+
+**Project:** DocumentService (DOC)  
+**Ticket:** DOC-1 - GDPicture and Nutrient Replacing  
+**Owner:** Hakan Tek  
+**Date:** July 3, 2026
+
+---
+
+## Overview
+
+This specification defines the controller structure and REST API endpoints for the DocumentService service.
+
+---
+
+## PdfValidationController
+
+### Endpoint: PDF Validation
+**Route:** `POST /api/pdf/validation/validate`  
+**Function:** Checks whether the file is a valid PDF, whether it is corrupted, and returns basic information
+
+**Input:**
+- PDF file (multipart/form-data)
+
+**Output:**
+```json
+{
+  "isValid": bool,
+  "pdfVersion": string,
+  "pageCount": int,
+  "fileSize": long,
+  "encrypted": bool,
+  "errors": string[]
+}
+```
+
+**Usage:** All products - basic PDF input check
+
+---
+
+### Endpoint: PDF/A Validation
+**Route:** `POST /api/pdf/validation/validate-pdfa`  
+**Function:** PDF/A conformance check (embedded fonts, encryption, JavaScript, etc.)
+
+**Input:**
+- PDF file (multipart/form-data)
+
+**Output:**
+```json
+{
+  "isValid": bool,
+  "pdfaVersion": string,
+  "pageCount": int,
+  "errors": string[],
+  "warnings": string[]
+}
+```
+
+**Usage:** taskFLOW, eParser - ensuring PDF/A conformance
+
+---
+
+## PdfAttachmentController
+
+### Endpoint: Attachment Check
+**Route:** `POST /api/pdf/attachments/check`  
+**Function:** Detects whether embedded files (e.g. ZUGFeRD XML) are present in the PDF
+
+**Input:**
+- PDF file (multipart/form-data)
+
+**Output:**
+```json
+{
+  "hasAttachments": bool,
+  "attachmentCount": int,
+  "attachments": [
+    {
+      "fileName": string,
+      "mimeType": string,
+      "size": long
+    }
+  ]
+}
+```
+
+**Usage:** eParser (ZUGFeRD), ErgebnisberichtCreator
+
+---
+
+### Endpoint: Attachment Extraction
+**Route:** `POST /api/pdf/attachments/extract`  
+**Function:** Extracts all embedded files from the PDF and returns them as a ZIP archive
+
+**Input:**
+- PDF file (multipart/form-data)
+
+**Output:**
+- Binary stream (application/zip)
+- Content-Disposition: attachment; filename="attachments.zip"
+- ZIP archive containing all extracted files
+
+**Usage:** eParser (ZUGFeRD XML extraction)
+
+---
+
+### Endpoint: Add Attachment
+**Route:** `POST /api/pdf/attachments/add`  
+**Function:** Embeds one or more files as attachments in a PDF (supports PDF/A-3)
+
+**Input:**
+- PDF file (multipart/form-data)
+- Attachment files (multipart/form-data, multiple)
+
+**Output:**
+- Binary stream (application/pdf)
+- Content-Disposition: attachment; filename="with-attachments.pdf"
+- PDF with embedded attachments
+
+**Usage:** eParser (ZUGFeRD XML embedding), PDF/A-3 archiving
+
+---
+
+## PdfOperationsController
+
+### Endpoint: PDF Merge
+**Route:** `POST /api/pdf/operations/merge`  
+**Function:** Merges multiple PDFs into a single file
+
+**Input:**
+- Multiple PDF files (multipart/form-data)
+- Field name: "files" (array of IFormFile)
+
+**Output:**
+- Binary stream (application/pdf)
+- Content-Disposition: attachment; filename="merged.pdf"
+- Merged PDF document
+
+**Usage:** signFLOW (Envelope Generator), ErgebnisberichtCreator, ResultHandler (windream)
+
+---
+
+### Endpoint: PDF Stamp
+**Route:** `POST /api/pdf/operations/stamp`  
+**Function:** Adds stamps to PDF pages (APPROVED, CONFIDENTIAL, etc.)
+
+**Input:**
+- PDF file (multipart/form-data)
+- Stamp configuration (JSON):
+  ```json
+  {
+    "text": string,
+    "position": string,
+    "pages": string,
+    "color": string,
+    "opacity": float
+  }
+  ```
+
+**Output:**
+- Binary stream (application/pdf)
+- Content-Disposition: attachment; filename="stamped.pdf"
+- PDF with applied stamps
+
+**Usage:** ErgebnisberichtCreator
+
+---
+
+### Endpoint: PDF Annotate
+**Route:** `POST /api/pdf/operations/annotate`  
+**Function:** Adds comments, highlights, and markings to the PDF
+
+**Input:**
+- PDF file (multipart/form-data)
+- Annotations (JSON):
+  ```json
+  {
+    "annotations": [
+      {
+        "type": string,
+        "page": int,
+        "position": object,
+        "text": string
+      }
+    ]
+  }
+  ```
+
+**Output:**
+- Binary stream (application/pdf)
+- Content-Disposition: attachment; filename="annotated.pdf"
+- PDF with applied annotations
+
+**Usage:** signFLOW (Envelope Generator)
+
+---
+
+## SwissQrCodeController
+
+### Endpoint: Swiss QR Code Extraction
+**Route:** `POST /api/swissqrcode/extract`  
+**Function:** Extracts and parses Swiss QR Bill (Swiss QR Code) from PDF
+
+**Input:**
+- PDF file (multipart/form-data)
+
+**Output:**
+```json
+{
+  "qrType": "SwissQrBill",
+  "version": "0200",
+  "creditorIban": "CH4431999123000889012",
+  "creditorName": "Example AG",
+  "creditorAddress": {
+    "addressType": "Structured",
+    "street": "Musterstrasse",
+    "houseNumber": "1",
+    "postalCode": "8000",
+    "city": "Zürich",
+    "country": "CH"
+  },
+  "amount": 1234.56,
+  "currency": "CHF",
+  "debtorName": "Max Mustermann",
+  "debtorAddress": { ... },
+  "referenceType": "QRR",
+  "reference": "210000000003139471430009017",
+  "unstructuredMessage": "Invoice #12345",
+  "billInformation": "//S1/10/12345",
+  "alternativeProcedures": ["UV1", "UV2"]
+}
+```
+
+**Usage:** eParser (Swiss QR Bill processing), signFLOW (payment reference extraction)
+
+**Note:** Supports only Structured Address (S-Type) as per Swiss QR Bill Standard 2.0. Combined Address (K-Type) deprecated November 21, 2025.
+
+---
+
+## PdfRenderController
+
+**Status:** REMOVED - PDF preview functionality will be implemented in .NET client library using DevExpress WinForms/WPF controls. Server-side rendering is unnecessary CPU/memory overhead.
+
+---
+
+## PdfConversionController
+
+### Endpoint: Convert PDF to PDF/A
+**Route:** `POST /api/pdf/conversion/to-pdfa`  
+**Function:** Converts a standard PDF to PDF/A
+
+**Input:**
+- PDF file (multipart/form-data)
+- PDF/A level (query parameter): "PDF/A-1b", "PDF/A-2b", "PDF/A-3b"
+
+**Output:**
+- Binary stream (application/pdf)
+- Content-Disposition: attachment; filename="converted-pdfa.pdf"
+- PDF/A compliant document
+
+**Usage:** taskFLOW (optional conversion)
+
+---
+
+### Endpoint: Convert PDF/A to PDF
+**Route:** `POST /api/pdf/conversion/from-pdfa`  
+**Function:** Converts PDF/A to a standard PDF
+
+**Input:**
+- PDF/A file (multipart/form-data)
+
+**Output:**
+- Binary stream (application/pdf)
+- Content-Disposition: attachment; filename="converted-pdf.pdf"
+- Standard PDF document
+
+**Usage:** taskFLOW (optional conversion)
+
+---
+
+## Technical Specifications
+
+### Framework Support
+- ✓ .NET Core (3.1+, 6.0+, 8.0+)
+- ✓ .NET Framework (4.7.2+, 4.8+)
+
+### Client Usage
+The service can be used on the client side **without manual HTTP response handling**:
+- Provide REST client wrapper
+- SDK for C# clients
+- Automatic serialization/deserialization
+- Abstracted error handling
+
+**Example Client SDK:**
+```csharp
+var client = new DocumentServiceClient("https://api.example.com");
+var result = await client.Pdf.Validation.ValidateAsync(pdfFile);
+if (result.IsValid) { ... }
+```
+
+### Response Format
+- Default: JSON (for metadata endpoints like validation, check)
+- Binary streams: application/pdf, application/zip (for operations, conversion, extraction)
+- Content-Disposition header: attachment; filename="<output-filename>"
+- Errors: HTTP Status Codes (400, 404, 500) + JSON error object
+- Success: HTTP 200 + JSON/Binary response
+
+**Binary Stream Endpoints:**
+- PDF Operations: merge, stamp, annotate
+- PDF Conversion: to-pdfa, from-pdfa
+- Attachment Operations: extract (ZIP), add (PDF)
+
+**JSON Response Endpoints:**
+- PDF Validation: validate, validate-pdfa
+- Attachment Check: check
+- Swiss QR Code: extract
+
+### Authentication
+- API Key (Header: `X-API-Key`)
+- Optional: OAuth2/JWT for advanced scenarios
+
+### Swagger/OpenAPI
+- Complete API documentation
+- Interactive test UI
+- Code generation for clients
+
+---
+
+## Prioritization
+
+### Phase 1 (Priority)
+1. PdfValidationController - both endpoints (validate, validate-pdfa)
+2. PdfAttachmentController - check endpoint
+3. SwissQrCodeController - extract endpoint (already implemented)
+4. PdfAttachmentController - extract endpoint
+5. PdfOperationsController - merge endpoint
+
+### Phase 2
+6. PdfOperationsController - stamp & annotate endpoints
+7. PdfAttachmentController - add attachment endpoint
+
+### Phase 3
+8. PdfConversionController - both endpoints (to-pdfa, from-pdfa)
+
+### Removed
+- PdfRenderController - moved to .NET client library (WinForms/WPF DevExpress controls)
+
+---
+
+**Last Updated:** July 3, 2026  
+**Author:** Hakan Tek  
+**Status:** Draft - Awaiting Feedback

DocumentOperator.API/Configuration/SerilogConfiguration.cs

@@ -1,6 +0,0 @@
-namespace DocumentOperator.API.Configuration
-{
-    public class SerilogConfiguration
-    {
-    }
-}

DocumentOperator.API/Configuration/SwaggerConfiguration.cs

@@ -1,6 +0,0 @@
-namespace DocumentOperator.API.Configuration
-{
-    public class SwaggerConfiguration
-    {
-    }
-}

DocumentOperator.API/DocumentOperator.API.csproj

@@ -1,24 +0,0 @@
-<Project Sdk="Microsoft.NET.Sdk.Web">
-
-  <PropertyGroup>
-    <TargetFramework>net8.0</TargetFramework>
-    <Nullable>enable</Nullable>
-    <ImplicitUsings>enable</ImplicitUsings>
-  </PropertyGroup>
-
-  <ItemGroup>
-    <PackageReference Include="Asp.Versioning.Http" Version="8.1.1" />
-    <PackageReference Include="Microsoft.Extensions.Caching.StackExchangeRedis" Version="8.0.28" />
-    <PackageReference Include="Serilog.AspNetCore" Version="10.0.0" />
-    <PackageReference Include="Serilog.Enrichers.Environment" Version="3.0.1" />
-    <PackageReference Include="Serilog.Sinks.File" Version="7.0.0" />
-    <PackageReference Include="Swashbuckle.AspNetCore" Version="6.6.2" />
-  </ItemGroup>
-
-  <ItemGroup>
-    <ProjectReference Include="..\DocumentOperator.Application\DocumentOperator.Application.csproj" />
-    <ProjectReference Include="..\DocumentOperator.Domain\DocumentOperator.Domain.csproj" />
-    <ProjectReference Include="..\DocumentOperator.Infrastructure\DocumentOperator.Infrastructure.csproj" />
-  </ItemGroup>
-
-</Project>

DocumentOperator.API/DocumentOperator.API.http

@@ -1,6 +0,0 @@
-@DocumentOperator.API_HostAddress = http://localhost:5028
-
-GET {{DocumentOperator.API_HostAddress}}/weatherforecast/
-Accept: application/json
-
-###

DocumentOperator.API/Endpoints/v1/DocumentEndpoints.cs

@@ -1,6 +0,0 @@
-namespace DocumentOperator.API.Endpoints.v1
-{
-    public class DocumentEndpoints
-    {
-    }
-}

DocumentOperator.API/Middleware/ExceptionHandlingMiddleware.cs

@@ -1,6 +0,0 @@
-namespace DocumentOperator.API.Middleware
-{
-    public class ExceptionHandlingMiddleware
-    {
-    }
-}

DocumentOperator.API/Middleware/RequestLoggingMiddleware.cs

@@ -1,6 +0,0 @@
-namespace DocumentOperator.API.Middleware
-{
-    public class RequestLoggingMiddleware
-    {
-    }
-}

DocumentOperator.API/Middleware/TenantResolutionMiddleware.cs

@@ -1,6 +0,0 @@
-namespace DocumentOperator.API.Middleware
-{
-    public class TenantResolutionMiddleware
-    {
-    }
-}

DocumentOperator.API/Program.cs

@@ -1,72 +0,0 @@
-using Serilog;
-using DocumentOperator.Infrastructure.Configuration;
-
-var builder = WebApplication.CreateBuilder(args);
-
-// ========================================
-// 1. Serilog Configuration
-// ========================================
-Log.Logger = new LoggerConfiguration()
-    .ReadFrom.Configuration(builder.Configuration)
-    .Enrich.FromLogContext()
-    .Enrich.WithProperty("Application", "DocumentOperator")
-    .CreateLogger();
-
-builder.Host.UseSerilog();
-
-Log.Information("Starting DocumentOperator API...");
-
-try
-{
-    // ========================================
-    // 2. Options Pattern Configuration
-    // ========================================
-    builder.Services.Configure<DocumentOperatorSettings>(
-        builder.Configuration.GetSection(DocumentOperatorSettings.SectionName));
-
-    builder.Services.Configure<RedisSettings>(
-        builder.Configuration.GetSection(RedisSettings.SectionName));
-
-    builder.Services.Configure<ApiKeySettings>(
-        builder.Configuration.GetSection(ApiKeySettings.SectionName));
-
-    // ========================================
-    // 3. Services
-    // ========================================
-    builder.Services.AddControllers();
-    builder.Services.AddEndpointsApiExplorer();
-    builder.Services.AddSwaggerGen();
-
-    // ========================================
-    // 4. Build App
-    // ========================================
-    var app = builder.Build();
-
-    // ========================================
-    // 5. Middleware Pipeline
-    // ========================================
-    if (app.Environment.IsDevelopment())
-    {
-        app.UseSwagger();
-        app.UseSwaggerUI();
-    }
-
-    app.UseSerilogRequestLogging(); // Log HTTP Requests
-
-    app.UseHttpsRedirection();
-    app.UseAuthorization();
-    app.MapControllers();
-
-    Log.Information("DocumentOperator API started successfully");
-
-    app.Run();
-}
-catch (Exception ex)
-{
-    Log.Fatal(ex, "Application startup failed");
-    throw;
-}
-finally
-{
-    Log.CloseAndFlush();
-}

DocumentOperator.API/appsettings.json

@@ -1,66 +0,0 @@
-{
-  "Logging": {
-    "LogLevel": {
-      "Default": "Information",
-      "Microsoft.AspNetCore": "Warning"
-    }
-  },
-  "AllowedHosts": "*",
-
-  "Serilog": {
-    "MinimumLevel": {
-      "Default": "Information",
-      "Override": {
-        "Microsoft": "Warning",
-        "Microsoft.AspNetCore": "Warning",
-        "System": "Warning"
-      }
-    },
-    "WriteTo": [
-      {
-        "Name": "Console",
-        "Args": {
-          "outputTemplate": "[{Timestamp:HH:mm:ss} {Level:u3}] {Message:lj} {Properties:j}{NewLine}{Exception}"
-        }
-      },
-      {
-        "Name": "File",
-        "Args": {
-          "path": "Logs/log-.txt",
-          "rollingInterval": "Day",
-          "outputTemplate": "{Timestamp:yyyy-MM-dd HH:mm:ss.fff zzz} [{Level:u3}] {Message:lj} {Properties:j}{NewLine}{Exception}"
-        }
-      }
-    ],
-    "Enrich": [ "FromLogContext", "WithMachineName", "WithThreadId" ]
-  },
-
-  "DocumentOperatorSettings": {
-    "TempFolderPath": "C:\\Temp\\DocumentOperator",
-    "TempFileRetentionHours": 24,
-    "MaxPdfSizeMB": 50,
-    "EnableDetailedLogging": true
-  },
-
-  "RedisSettings": {
-    "ConnectionString": "localhost:6379",
-    "InstanceName": "DocumentOperator:",
-    "CacheExpirationMinutes": 60
-  },
-
-  "ApiKeySettings": {
-    "EnableValidation": true,
-    "Keys": {
-      "customer-a-key-12345": {
-        "TenantId": "customer-a",
-        "TenantName": "Customer A GmbH",
-        "IsActive": true
-      },
-      "customer-b-key-67890": {
-        "TenantId": "customer-b",
-        "TenantName": "Customer B AG",
-        "IsActive": true
-      }
-    }
-  }
-}

DocumentOperator.Application/DocumentOperator.Application.csproj

@@ -1,32 +0,0 @@
-<Project Sdk="Microsoft.NET.Sdk">
-
-  <PropertyGroup>
-    <TargetFramework>net8.0</TargetFramework>
-    <ImplicitUsings>enable</ImplicitUsings>
-    <Nullable>enable</Nullable>
-  </PropertyGroup>
-
-  <ItemGroup>
-    <PackageReference Include="FluentValidation" Version="12.1.1" />
-    <PackageReference Include="FluentValidation.DependencyInjectionExtensions" Version="12.1.1" />
-    <PackageReference Include="MediatR" Version="14.1.0" />
-  </ItemGroup>
-
-  <ItemGroup>
-    <ProjectReference Include="..\DocumentOperator.Domain\DocumentOperator.Domain.csproj" />
-  </ItemGroup>
-
-  <ItemGroup>
-    <Folder Include="Common\Interfaces\" />
-    <Folder Include="Common\Behaviors\" />
-    <Folder Include="Common\DTOs\" />
-    <Folder Include="Common\Mappings\" />
-    <Folder Include="DependencyInjection\" />
-    <Folder Include="Features\Documents\ExtractAttachments\" />
-    <Folder Include="Features\Documents\ConcatenatePdfs\" />
-    <Folder Include="Features\Documents\ApplyStamp\" />
-    <Folder Include="Features\Documents\EmbedCertificate\" />
-    <Folder Include="Features\Documents\ValidatePdf\" />
-  </ItemGroup>
-
-</Project>

DocumentOperator.Application/Features/Documents/ProcessDocument/ProcessDocumentCommand.cs

@@ -1,12 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace DocumentOperator.Application.Features.Documents.ProcessDocument
-{
-    internal class ProcessDocumentCommand
-    {
-    }
-}

DocumentOperator.Application/Features/Documents/ProcessDocument/ProcessDocumentHandler.cs

@@ -1,12 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace DocumentOperator.Application.Features.Documents.ProcessDocument
-{
-    internal class ProcessDocumentHandler
-    {
-    }
-}

DocumentOperator.Application/Features/Documents/ProcessDocument/ProcessDocumentValidator.cs

@@ -1,12 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace DocumentOperator.Application.Features.Documents.ProcessDocument
-{
-    internal class ProcessDocumentValidator
-    {
-    }
-}

DocumentOperator.Domain/Common/Exceptions/NotFoundException.cs

@@ -1,25 +0,0 @@
-namespace DocumentOperator.Domain.Common.Exceptions;
-
-/// <summary>
-/// Exception thrown when a requested resource is not found.
-/// Maps to HTTP 404 Not Found in the API layer.
-/// </summary>
-public class NotFoundException : DomainException
-{
-    public string ResourceType { get; }
-    public object ResourceId { get; }
-
-    public NotFoundException(string resourceType, object resourceId)
-        : base($"{resourceType} with ID '{resourceId}' was not found.", "RESOURCE_NOT_FOUND")
-    {
-        ResourceType = resourceType;
-        ResourceId = resourceId;
-    }
-
-    public NotFoundException(string resourceType, object resourceId, string customMessage)
-        : base(customMessage, "RESOURCE_NOT_FOUND")
-    {
-        ResourceType = resourceType;
-        ResourceId = resourceId;
-    }
-}

DocumentOperator.Domain/Common/Exceptions/PdfProcessingException.cs

@@ -1,34 +0,0 @@
-namespace DocumentOperator.Domain.Common.Exceptions;
-
-/// <summary>
-/// Exception thrown when PDF processing operations fail.
-/// Maps to HTTP 500 Internal Server Error or 422 Unprocessable Entity in the API layer.
-/// </summary>
-public class PdfProcessingException : DomainException
-{
-    public string Operation { get; }
-
-    public PdfProcessingException(string operation, string message)
-        : base($"PDF processing failed during '{operation}': {message}", "PDF_PROCESSING_ERROR")
-    {
-        Operation = operation;
-    }
-
-    public PdfProcessingException(string operation, string message, Exception innerException)
-        : base($"PDF processing failed during '{operation}': {message}", "PDF_PROCESSING_ERROR", innerException)
-    {
-        Operation = operation;
-    }
-
-    public PdfProcessingException(string message)
-        : base(message, "PDF_PROCESSING_ERROR")
-    {
-        Operation = "Unknown";
-    }
-
-    public PdfProcessingException(string message, Exception innerException)
-        : base(message, "PDF_PROCESSING_ERROR", innerException)
-    {
-        Operation = "Unknown";
-    }
-}

DocumentOperator.Domain/Models/Enums/DocumentOperationType.cs

@@ -1,10 +0,0 @@
-namespace DocumentOperator.Domain.Models.Enums;
-
-public enum DocumentOperationType
-{
-    Validate,
-    ExtractAttachments,
-    Concatenate,
-    ApplyStamp,
-    EmbedCertificate
-}

DocumentOperator.Domain/Models/Enums/ProcessingStatus.cs

@@ -1,9 +0,0 @@
-namespace DocumentOperator.Domain.Models.Enums;
-
-public enum ProcessingStatus
-{
-    Pending,
-    Processing,
-    Success,
-    Failed
-}

DocumentOperator.Infrastructure/DocumentOperator.Infrastructure.csproj

@@ -1,26 +0,0 @@
-<Project Sdk="Microsoft.NET.Sdk">
-
-  <PropertyGroup>
-    <TargetFramework>net8.0</TargetFramework>
-    <ImplicitUsings>enable</ImplicitUsings>
-    <Nullable>enable</Nullable>
-  </PropertyGroup>
-
-  <ItemGroup>
-    <PackageReference Include="DevExpress.Pdf.Core" Version="25.2.8" />
-    <PackageReference Include="Microsoft.Extensions.Options.ConfigurationExtensions" Version="8.0.0" />
-  </ItemGroup>
-
-  <ItemGroup>
-    <ProjectReference Include="..\DocumentOperator.Application\DocumentOperator.Application.csproj" />
-    <ProjectReference Include="..\DocumentOperator.Domain\DocumentOperator.Domain.csproj" />
-  </ItemGroup>
-
-  <ItemGroup>
-    <Folder Include="DependencyInjection\" />
-    <Folder Include="Services\FileStorage\" />
-    <Folder Include="Services\DocumentValidation\" />
-    <Folder Include="Services\PdfProcessing\" />
-  </ItemGroup>
-
-</Project>

DocumentOperator.sln

@@ -1,43 +0,0 @@
-
-Microsoft Visual Studio Solution File, Format Version 12.00
-# Visual Studio Version 17
-VisualStudioVersion = 17.14.37328.6
-MinimumVisualStudioVersion = 10.0.40219.1
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "DocumentOperator.API", "DocumentOperator.API\DocumentOperator.API.csproj", "{BA41F6A2-EE29-48F9-A3CB-29A05E57CF30}"
-EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "DocumentOperator.Application", "DocumentOperator.Application\DocumentOperator.Application.csproj", "{B2B735FC-5F39-4CFF-9C54-C4F8820880B6}"
-EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "DocumentOperator.Infrastructure", "DocumentOperator.Infrastructure\DocumentOperator.Infrastructure.csproj", "{C4CA19A8-8168-453B-B4ED-77E032CFE52E}"
-EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "DocumentOperator.Domain", "DocumentOperator.Domain\DocumentOperator.Domain.csproj", "{B4C1C3ED-D3E8-4272-8704-2E73CEA6A0DD}"
-EndProject
-Global
-	GlobalSection(SolutionConfigurationPlatforms) = preSolution
-		Debug|Any CPU = Debug|Any CPU
-		Release|Any CPU = Release|Any CPU
-	EndGlobalSection
-	GlobalSection(ProjectConfigurationPlatforms) = postSolution
-		{BA41F6A2-EE29-48F9-A3CB-29A05E57CF30}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{BA41F6A2-EE29-48F9-A3CB-29A05E57CF30}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{BA41F6A2-EE29-48F9-A3CB-29A05E57CF30}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{BA41F6A2-EE29-48F9-A3CB-29A05E57CF30}.Release|Any CPU.Build.0 = Release|Any CPU
-		{B2B735FC-5F39-4CFF-9C54-C4F8820880B6}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{B2B735FC-5F39-4CFF-9C54-C4F8820880B6}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{B2B735FC-5F39-4CFF-9C54-C4F8820880B6}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{B2B735FC-5F39-4CFF-9C54-C4F8820880B6}.Release|Any CPU.Build.0 = Release|Any CPU
-		{C4CA19A8-8168-453B-B4ED-77E032CFE52E}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{C4CA19A8-8168-453B-B4ED-77E032CFE52E}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{C4CA19A8-8168-453B-B4ED-77E032CFE52E}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{C4CA19A8-8168-453B-B4ED-77E032CFE52E}.Release|Any CPU.Build.0 = Release|Any CPU
-		{B4C1C3ED-D3E8-4272-8704-2E73CEA6A0DD}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{B4C1C3ED-D3E8-4272-8704-2E73CEA6A0DD}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{B4C1C3ED-D3E8-4272-8704-2E73CEA6A0DD}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{B4C1C3ED-D3E8-4272-8704-2E73CEA6A0DD}.Release|Any CPU.Build.0 = Release|Any CPU
-	EndGlobalSection
-	GlobalSection(SolutionProperties) = preSolution
-		HideSolutionNode = FALSE
-	EndGlobalSection
-	GlobalSection(ExtensibilityGlobals) = postSolution
-		SolutionGuid = {832CA90A-06D6-4312-9B35-16CC665EB37C}
-	EndGlobalSection
-EndGlobal

DocumentService.API/Configuration/DualInputDocumentFilter.cs

@@ -0,0 +1,125 @@
+using Microsoft.AspNetCore.Mvc.ApiExplorer;
+using Microsoft.OpenApi.Models;
+using Swashbuckle.AspNetCore.SwaggerGen;
+
+namespace DocumentService.API.Configuration
+{
+    /// <summary>
+    /// Swagger document filter that merges operations with same path but different [Consumes] attributes.
+    /// Ensures both multipart/form-data and application/json variants are visible in Swagger UI.
+    /// </summary>
+    public class DualInputDocumentFilter : IDocumentFilter
+    {
+        private readonly IApiDescriptionGroupCollectionProvider _apiDescriptionProvider;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="DualInputDocumentFilter"/> class.
+        /// </summary>
+        /// <param name="apiDescriptionProvider">API description provider to access all endpoints</param>
+        public DualInputDocumentFilter(IApiDescriptionGroupCollectionProvider apiDescriptionProvider)
+        {
+            _apiDescriptionProvider = apiDescriptionProvider;
+        }
+
+        /// <summary>
+        /// Applies the filter to merge operations with different content types.
+        /// </summary>
+        public void Apply(OpenApiDocument swaggerDoc, DocumentFilterContext context)
+        {
+            var allApiDescriptions = _apiDescriptionProvider.ApiDescriptionGroups.Items
+                .SelectMany(g => g.Items)
+                .ToList();
+
+            // Group by path
+            var groupedByPath = allApiDescriptions
+                .GroupBy(x => "/" + x.RelativePath)
+                .ToList();
+
+            foreach (var group in groupedByPath)
+            {
+                var path = group.Key;
+
+                if (!swaggerDoc.Paths.ContainsKey(path))
+                    continue;
+
+                var pathItem = swaggerDoc.Paths[path];
+
+                // Find multipart and JSON variants
+                var multipartDesc = group.FirstOrDefault(x =>
+                    x.SupportedRequestFormats.Any(f => f.MediaType == "multipart/form-data"));
+
+                var jsonDesc = group.FirstOrDefault(x =>
+                    x.SupportedRequestFormats.Any(f => f.MediaType == "application/json"));
+
+                // If we have both variants, merge them into single operation
+                if (multipartDesc != null && jsonDesc != null)
+                {
+                    var httpMethod = multipartDesc.HttpMethod?.ToLowerInvariant();
+                    OperationType operationType;
+
+                    if (!Enum.TryParse<OperationType>(httpMethod, true, out operationType))
+                        continue;
+
+                    if (!pathItem.Operations.ContainsKey(operationType))
+                        continue;
+
+                    var operation = pathItem.Operations[operationType];
+
+                    // Ensure RequestBody exists
+                    if (operation.RequestBody == null)
+                    {
+                        operation.RequestBody = new OpenApiRequestBody
+                        {
+                            Required = true,
+                            Content = new Dictionary<string, OpenApiMediaType>()
+                        };
+                    }
+
+                    // Add multipart/form-data if missing
+                    if (!operation.RequestBody.Content.ContainsKey("multipart/form-data"))
+                    {
+                        operation.RequestBody.Content.Add("multipart/form-data", new OpenApiMediaType
+                        {
+                            Schema = new OpenApiSchema
+                            {
+                                Type = "object",
+                                Properties = new Dictionary<string, OpenApiSchema>
+                                {
+                                    ["file"] = new OpenApiSchema
+                                    {
+                                        Type = "string",
+                                        Format = "binary",
+                                        Description = "PDF file to upload"
+                                    }
+                                },
+                                Required = new HashSet<string> { "file" }
+                            }
+                        });
+                    }
+
+                    // Add application/json if missing
+                    if (!operation.RequestBody.Content.ContainsKey("application/json"))
+                    {
+                        operation.RequestBody.Content.Add("application/json", new OpenApiMediaType
+                        {
+                            Schema = new OpenApiSchema
+                            {
+                                Type = "object",
+                                Properties = new Dictionary<string, OpenApiSchema>
+                                {
+                                    ["base64Pdf"] = new OpenApiSchema
+                                    {
+                                        Type = "string",
+                                        Format = "byte",
+                                        Description = "Base64-encoded PDF file content"
+                                    }
+                                },
+                                Required = new HashSet<string> { "base64Pdf" }
+                            }
+                        });
+                    }
+                }
+            }
+        }
+    }
+}

DocumentService.API/Configuration/SerilogConfiguration.cs

@@ -0,0 +1,9 @@
+namespace DocumentService.API.Configuration
+{
+    /// <summary>
+    /// Placeholder class for Serilog configuration extensions.
+    /// </summary>
+    public class SerilogConfiguration
+    {
+    }
+}

DocumentService.API/Configuration/SwaggerConfiguration.cs

@@ -0,0 +1,50 @@
+using Microsoft.Extensions.Options;
+using Microsoft.OpenApi.Models;
+using System.Reflection;
+
+namespace DocumentService.API.Configuration
+{
+    /// <summary>
+    /// Provides extension methods for configuring Swagger/OpenAPI documentation.
+    /// </summary>
+    public static class SwaggerConfiguration
+    {
+        /// <summary>
+        /// Adds Swagger documentation generation to the service collection.
+        /// </summary>
+        /// <param name="services">The service collection to add Swagger to.</param>
+        /// <param name="configuration">Configuration to read SwaggerSettings from.</param>
+        /// <returns>The modified service collection.</returns>
+        public static IServiceCollection AddSwaggerDocumentation(
+            this IServiceCollection services,
+            IConfiguration configuration)
+        {
+            var swaggerSettings = configuration.GetSection(SwaggerSettings.SectionName).Get<SwaggerSettings>()
+                ?? new SwaggerSettings();
+
+            services.AddSwaggerGen(options =>
+            {
+                options.SwaggerDoc(swaggerSettings.Version, new OpenApiInfo
+                {
+                    Title = swaggerSettings.Title,
+                    Version = swaggerSettings.Version,
+                    Description = swaggerSettings.Description
+                });
+
+                // Resolve conflicting actions: Keep first variant
+                // DualInputDocumentFilter will merge both variants into single operation
+                options.ResolveConflictingActions(apiDescriptions => apiDescriptions.First());
+
+                // Add document filter to merge operations with different content types
+                options.DocumentFilter<DualInputDocumentFilter>();
+
+                // XML-Kommentare einbinden
+                var xmlFile = $"{Assembly.GetExecutingAssembly().GetName().Name}.xml";
+                var xmlPath = Path.Combine(AppContext.BaseDirectory, xmlFile);
+                options.IncludeXmlComments(xmlPath);
+            });
+
+            return services;
+        }
+    }
+}

DocumentService.API/Configuration/SwaggerSettings.cs

@@ -0,0 +1,33 @@
+namespace DocumentService.API.Configuration;
+
+/// <summary>
+/// Configuration settings for Swagger/OpenAPI documentation.
+/// </summary>
+public class SwaggerSettings
+{
+    /// <summary>
+    /// 
+    /// </summary>
+    public const string SectionName = "SwaggerSettings";
+
+    /// <summary>
+    /// Enable Swagger UI in Production environment.
+    /// Default: true (allows production testing/debugging).
+    /// </summary>
+    public bool EnableInProduction { get; set; } = true;
+
+    /// <summary>
+    /// API title displayed in Swagger UI.
+    /// </summary>
+    public string Title { get; set; } = "DocumentService API";
+
+    /// <summary>
+    /// API version.
+    /// </summary>
+    public string Version { get; set; } = "v1";
+
+    /// <summary>
+    /// API description displayed in Swagger UI.
+    /// </summary>
+    public string Description { get; set; } = "PDF document processing service";
+}

DocumentService.API/Controllers/PdfAttachmentController.cs

@@ -0,0 +1,292 @@
+using DocumentService.Application.AddAttachments;
+using DocumentService.Application.CheckPdfAttachments.Queries;
+using DocumentService.Application.Common.DTOs;
+using DocumentService.Application.ExtractPdfAttachments;
+using DocumentService.Application.Common.DTOs.Requests;
+using DocumentService.Domain.Common.Exceptions;
+using MediatR;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Mvc;
+
+namespace DocumentService.API.Controllers;
+
+/// <summary>
+/// Controller for PDF attachment operations (detection, extraction, embedding)
+/// </summary>
+[ApiController]
+[Route("api/pdf/attachments")]
+[Produces("application/json")]
+public class PdfAttachmentController(IMediator mediator) : ControllerBase
+{
+    /// <summary>
+    /// Checks if a PDF contains embedded files (attachments) and returns their metadata.
+    /// Supports multipart/form-data file upload.
+    /// </summary>
+    /// <param name="file">The PDF file to check for attachments</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>Attachment check result with metadata for all found attachments</returns>
+    /// <response code="200">PDF successfully checked - returns attachment details</response>
+    /// <response code="400">Invalid input (file missing, not a PDF, or corrupted)</response>
+    /// <response code="500">Internal server error during PDF processing</response>
+    [HttpPost("check")]
+    [Consumes("multipart/form-data")]
+    [ProducesResponseType(typeof(AttachmentCheckResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> CheckAttachmentsFromFile(
+        IFormFile file,
+        CancellationToken cancellationToken)
+    {
+        // Use IFormFile stream directly (no intermediate byte[] conversion)
+        using var pdfStream = file.OpenReadStream();
+
+        // Send query to MediatR (ValidationBehavior runs automatically)
+        var query = new CheckPdfAttachmentsQuery { PdfStream = pdfStream };
+        var result = await mediator.Send(query, cancellationToken);
+
+        return Ok(result);
+    }
+
+    /// <summary>
+    /// Checks if a PDF contains embedded files (attachments) and returns their metadata.
+    /// Supports Base64-encoded PDF via JSON payload.
+    /// </summary>
+    /// <param name="request">Request containing Base64-encoded PDF</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>Attachment check result with metadata for all found attachments</returns>
+    /// <response code="200">PDF successfully checked - returns attachment details</response>
+    /// <response code="400">Invalid input (Base64 format error, not a PDF, or corrupted)</response>
+    /// <response code="500">Internal server error during PDF processing</response>
+    [HttpPost("check")]
+    [Consumes("application/json")]
+    [ProducesResponseType(typeof(AttachmentCheckResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> CheckAttachmentsFromBase64(
+        [FromBody] CheckPdfAttachmentsRequest request,
+        CancellationToken cancellationToken)
+    {
+        // Convert Base64 to stream (wrap in try-catch to throw BadRequestException)
+        byte[] pdfBytes;
+        try
+        {
+            pdfBytes = Convert.FromBase64String(request.Base64Pdf);
+        }
+        catch (FormatException ex)
+        {
+            throw new BadRequestException("Invalid Base64 format: " + ex.Message);
+        }
+        
+        using var pdfStream = new MemoryStream(pdfBytes);
+        
+        // Send query to MediatR (ValidationBehavior runs automatically)
+        var query = new CheckPdfAttachmentsQuery { PdfStream = pdfStream };
+        var result = await mediator.Send(query, cancellationToken);
+
+        return Ok(result);
+    }
+
+    /// <summary>
+    /// Extracts all embedded files from a PDF and returns them as a ZIP archive.
+    /// Supports multipart/form-data file upload.
+    /// </summary>
+    /// <param name="file">The PDF file to extract attachments from</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>ZIP archive containing all extracted attachments</returns>
+    /// <response code="200">Attachments extracted successfully - returns ZIP file</response>
+    /// <response code="400">Invalid input (file missing, not a PDF, or corrupted)</response>
+    /// <response code="404">PDF contains no attachments</response>
+    /// <response code="500">Internal server error during PDF processing</response>
+    [HttpPost("extract")]
+    [Consumes("multipart/form-data")]
+    [ProducesResponseType(typeof(FileContentResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status404NotFound)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> ExtractAttachmentsFromFile(
+        IFormFile file,
+        CancellationToken cancellationToken)
+    {
+        // Use IFormFile stream directly (no intermediate byte[] conversion)
+        using var pdfStream = file.OpenReadStream();
+
+        // Send command to MediatR
+        var command = new ExtractPdfAttachmentsCommand { PdfStream = pdfStream };
+        byte[] zipBytes = await mediator.Send(command, cancellationToken);
+
+        // Return ZIP file
+        return File(zipBytes, "application/zip", "attachments.zip");
+    }
+
+    /// <summary>
+    /// Extracts all embedded files from a PDF and returns them as a ZIP archive.
+    /// Supports Base64-encoded PDF via JSON payload.
+    /// </summary>
+    /// <param name="request">Request containing Base64-encoded PDF</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>ZIP archive containing all extracted attachments</returns>
+    /// <response code="200">Attachments extracted successfully - returns ZIP file</response>
+    /// <response code="400">Invalid input (Base64 format error, not a PDF, or corrupted)</response>
+    /// <response code="404">PDF contains no attachments</response>
+    /// <response code="500">Internal server error during PDF processing</response>
+    [HttpPost("extract")]
+    [Consumes("application/json")]
+    [ProducesResponseType(typeof(FileContentResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status404NotFound)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> ExtractAttachmentsFromBase64(
+        [FromBody] ExtractPdfAttachmentsRequest request,
+        CancellationToken cancellationToken)
+    {
+        // Convert Base64 to stream (wrap in try-catch to throw BadRequestException)
+        byte[] pdfBytes;
+        try
+        {
+            pdfBytes = Convert.FromBase64String(request.Base64Pdf);
+        }
+        catch (FormatException ex)
+        {
+            throw new BadRequestException("Invalid Base64 format: " + ex.Message);
+        }
+        
+        using var pdfStream = new MemoryStream(pdfBytes);
+
+        // Send command to MediatR
+        var command = new ExtractPdfAttachmentsCommand { PdfStream = pdfStream };
+        byte[] zipBytes = await mediator.Send(command, cancellationToken);
+
+        // Return ZIP file
+        return File(zipBytes, "application/zip", "attachments.zip");
+    }
+
+    /// <summary>
+    /// Embeds one or more files as attachments in a PDF document (supports PDF/A-3).
+    /// Supports multipart/form-data file upload.
+    /// </summary>
+    /// <param name="pdfFile">The PDF file to add attachments to</param>
+    /// <param name="attachmentFiles">Files to embed as attachments (one or more)</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>PDF with embedded attachments</returns>
+    /// <response code="200">Attachments added successfully - returns PDF</response>
+    /// <response code="400">Invalid input (file missing, not a PDF, or no attachments provided)</response>
+    /// <response code="500">Internal server error during PDF processing</response>
+    [Obsolete("This endpoint is not implemented yet.")]
+    [HttpPost("add")]
+    [Consumes("multipart/form-data")]
+    [ProducesResponseType(typeof(FileContentResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> AddAttachmentsFromFile(
+        IFormFile pdfFile,
+        List<IFormFile> attachmentFiles,
+        CancellationToken cancellationToken)
+    {
+        if (pdfFile == null || pdfFile.Length == 0)
+        {
+            throw new BadRequestException("PDF file is required");
+        }
+
+        if (attachmentFiles == null || attachmentFiles.Count == 0)
+        {
+            throw new BadRequestException("At least one attachment file is required");
+        }
+
+        // Use IFormFile stream directly (no intermediate byte[] conversion)
+        using var pdfStream = pdfFile.OpenReadStream();
+
+        // Convert attachment files to AttachmentFile records
+        var attachments = new List<AttachmentFile>();
+        foreach (var file in attachmentFiles)
+        {
+            using var ms = new MemoryStream();
+            await file.CopyToAsync(ms, cancellationToken);
+            
+            attachments.Add(new AttachmentFile
+            {
+                FileName = file.FileName,
+                Content = ms.ToArray(),
+                MimeType = file.ContentType
+            });
+        }
+
+        // Send command to MediatR
+        var command = new AddAttachmentsCommand 
+        { 
+            PdfStream = pdfStream,
+            Attachments = attachments
+        };
+        byte[] resultPdf = await mediator.Send(command, cancellationToken);
+
+        // Return PDF with attachments
+        return File(resultPdf, "application/pdf", "with-attachments.pdf");
+    }
+
+    /// <summary>
+    /// Embeds one or more files as attachments in a PDF document (supports PDF/A-3).
+    /// Supports Base64-encoded PDF and attachments via JSON payload.
+    /// </summary>
+    /// <param name="request">Request containing Base64-encoded PDF and attachments</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>PDF with embedded attachments</returns>
+    /// <response code="200">Attachments added successfully - returns PDF</response>
+    /// <response code="400">Invalid input (Base64 format error, not a PDF, or no attachments provided)</response>
+    /// <response code="500">Internal server error during PDF processing</response>
+    [Obsolete("This endpoint is not implemented yet.")]
+    [HttpPost("add")]
+    [Consumes("application/json")]
+    [ProducesResponseType(typeof(FileContentResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> AddAttachmentsFromBase64(
+        [FromBody] AddAttachmentsRequest request,
+        CancellationToken cancellationToken)
+    {
+        // Convert Base64 PDF to stream
+        byte[] pdfBytes;
+        try
+        {
+            pdfBytes = Convert.FromBase64String(request.Base64Pdf);
+        }
+        catch (FormatException ex)
+        {
+            throw new BadRequestException("Invalid Base64 PDF format: " + ex.Message);
+        }
+        
+        using var pdfStream = new MemoryStream(pdfBytes);
+
+        // Convert Base64 attachments to AttachmentFile records
+        var attachments = new List<AttachmentFile>();
+        foreach (var att in request.Attachments)
+        {
+            byte[] attBytes;
+            try
+            {
+                attBytes = Convert.FromBase64String(att.Base64Content);
+            }
+            catch (FormatException ex)
+            {
+                throw new BadRequestException($"Invalid Base64 format for attachment '{att.FileName}': " + ex.Message);
+            }
+
+            attachments.Add(new AttachmentFile
+            {
+                FileName = att.FileName,
+                Content = attBytes,
+                MimeType = att.MimeType
+            });
+        }
+
+        // Send command to MediatR
+        var command = new AddAttachmentsCommand 
+        { 
+            PdfStream = pdfStream,
+            Attachments = attachments
+        };
+        byte[] resultPdf = await mediator.Send(command, cancellationToken);
+
+        // Return PDF with attachments
+        return File(resultPdf, "application/pdf", "with-attachments.pdf");
+    }
+}
+

DocumentService.API/Controllers/PdfConversionController.cs

@@ -0,0 +1,182 @@
+using DocumentService.Application.ConvertFromPdfA;
+using DocumentService.Application.ConvertToPdfA;
+using DocumentService.Application.Common.DTOs.Requests;
+using DocumentService.Domain.Common.Exceptions;
+using MediatR;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Mvc;
+
+namespace DocumentService.API.Controllers;
+
+/// <summary>
+/// Controller for PDF conversion operations (PDF ? PDF/A)
+/// </summary>
+[ApiController]
+[Route("api/pdf/conversion")]
+[Obsolete("This endpoint is not implemented yet.")]
+public class PdfConversionController(IMediator mediator) : ControllerBase
+{
+    /// <summary>
+    /// Converts a standard PDF to PDF/A format.
+    /// Supports multipart/form-data file upload.
+    /// </summary>
+    /// <param name="file">The PDF file to convert</param>
+    /// <param name="pdfALevel">Target PDF/A level (e.g., "PDF/A-1b", "PDF/A-2b", "PDF/A-3b")</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>PDF/A compliant document</returns>
+    /// <response code="200">PDF converted to PDF/A successfully</response>
+    /// <response code="400">Invalid input (file missing, not a PDF, or invalid PDF/A level)</response>
+    /// <response code="500">Internal server error during PDF processing</response>
+    [Obsolete("This endpoint is not implemented yet.")]
+    [HttpPost("to-pdfa")]
+    [Consumes("multipart/form-data")]
+    [ProducesResponseType(typeof(FileContentResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> ConvertToPdfAFromFile(
+        IFormFile file,
+        [FromQuery] string pdfALevel = "PDF/A-3b",
+        CancellationToken cancellationToken = default)
+    {
+        if (file == null || file.Length == 0)
+        {
+            throw new BadRequestException("PDF file is required");
+        }
+
+        // Use IFormFile stream directly (no intermediate byte[] conversion)
+        using var pdfStream = file.OpenReadStream();
+
+        // Send command to MediatR
+        var command = new ConvertToPdfACommand 
+        { 
+            PdfStream = pdfStream,
+            PdfALevel = pdfALevel
+        };
+        byte[] resultPdf = await mediator.Send(command, cancellationToken);
+
+        // Return PDF/A file
+        return File(resultPdf, "application/pdf", "converted-pdfa.pdf");
+    }
+
+    /// <summary>
+    /// Converts a standard PDF to PDF/A format.
+    /// Supports Base64-encoded PDF via JSON payload.
+    /// </summary>
+    /// <param name="request">Request containing Base64-encoded PDF and PDF/A level</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>PDF/A compliant document</returns>
+    /// <response code="200">PDF converted to PDF/A successfully</response>
+    /// <response code="400">Invalid input (Base64 format error, not a PDF, or invalid PDF/A level)</response>
+    /// <response code="500">Internal server error during PDF processing</response>
+    [Obsolete("This endpoint is not implemented yet.")]
+    [HttpPost("to-pdfa")]
+    [Consumes("application/json")]
+    [ProducesResponseType(typeof(FileContentResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> ConvertToPdfAFromBase64(
+        [FromBody] ConvertToPdfARequest request,
+        CancellationToken cancellationToken = default)
+    {
+        // Convert Base64 PDF to stream
+        byte[] pdfBytes;
+        try
+        {
+            pdfBytes = Convert.FromBase64String(request.Base64Pdf);
+        }
+        catch (FormatException ex)
+        {
+            throw new BadRequestException("Invalid Base64 PDF format: " + ex.Message);
+        }
+        
+        using var pdfStream = new MemoryStream(pdfBytes);
+
+        // Send command to MediatR
+        var command = new ConvertToPdfACommand 
+        { 
+            PdfStream = pdfStream,
+            PdfALevel = request.PdfALevel ?? "PDF/A-3b"
+        };
+        byte[] resultPdf = await mediator.Send(command, cancellationToken);
+
+        // Return PDF/A file
+        return File(resultPdf, "application/pdf", "converted-pdfa.pdf");
+    }
+
+    /// <summary>
+    /// Converts a PDF/A document to a standard PDF (removes PDF/A restrictions).
+    /// Supports multipart/form-data file upload.
+    /// </summary>
+    /// <param name="file">The PDF/A file to convert</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>Standard PDF document</returns>
+    /// <response code="200">PDF/A converted to standard PDF successfully</response>
+    /// <response code="400">Invalid input (file missing, not a PDF)</response>
+    /// <response code="500">Internal server error during PDF processing</response>
+    [Obsolete("This endpoint is not implemented yet.")]
+    [HttpPost("from-pdfa")]
+    [Consumes("multipart/form-data")]
+    [ProducesResponseType(typeof(FileContentResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> ConvertFromPdfAFromFile(
+        IFormFile file,
+        CancellationToken cancellationToken = default)
+    {
+        if (file == null || file.Length == 0)
+        {
+            throw new BadRequestException("PDF/A file is required");
+        }
+
+        // Use IFormFile stream directly (no intermediate byte[] conversion)
+        using var pdfStream = file.OpenReadStream();
+
+        // Send command to MediatR
+        var command = new ConvertFromPdfACommand { PdfStream = pdfStream };
+        byte[] resultPdf = await mediator.Send(command, cancellationToken);
+
+        // Return standard PDF file
+        return File(resultPdf, "application/pdf", "converted-pdf.pdf");
+    }
+
+    /// <summary>
+    /// Converts a PDF/A document to a standard PDF (removes PDF/A restrictions).
+    /// Supports Base64-encoded PDF via JSON payload.
+    /// </summary>
+    /// <param name="request">Request containing Base64-encoded PDF/A</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>Standard PDF document</returns>
+    /// <response code="200">PDF/A converted to standard PDF successfully</response>
+    /// <response code="400">Invalid input (Base64 format error, not a PDF)</response>
+    /// <response code="500">Internal server error during PDF processing</response>
+    [Obsolete("This endpoint is not implemented yet.")]
+    [HttpPost("from-pdfa")]
+    [Consumes("application/json")]
+    [ProducesResponseType(typeof(FileContentResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> ConvertFromPdfAFromBase64(
+        [FromBody] ConvertFromPdfARequest request,
+        CancellationToken cancellationToken = default)
+    {
+        // Convert Base64 PDF to stream
+        byte[] pdfBytes;
+        try
+        {
+            pdfBytes = Convert.FromBase64String(request.Base64Pdf);
+        }
+        catch (FormatException ex)
+        {
+            throw new BadRequestException("Invalid Base64 PDF format: " + ex.Message);
+        }
+        
+        using var pdfStream = new MemoryStream(pdfBytes);
+
+        // Send command to MediatR
+        var command = new ConvertFromPdfACommand { PdfStream = pdfStream };
+        byte[] resultPdf = await mediator.Send(command, cancellationToken);
+
+        // Return standard PDF file
+        return File(resultPdf, "application/pdf", "converted-pdf.pdf");
+    }
+}

DocumentService.API/Controllers/PdfOperationsController.cs

@@ -0,0 +1,511 @@
+using DocumentService.Application.AddAnnotation;
+using DocumentService.Application.AddStamp;
+using DocumentService.Application.Common.DTOs.Requests;
+using DocumentService.Application.MergePdfs;
+using DocumentService.Domain.Common.Exceptions;
+using DocumentService.Domain.Models.ValueObjects;
+using MediatR;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Mvc;
+
+namespace DocumentService.API.Controllers;
+
+/// <summary>
+/// Controller for PDF operations (merge, stamp, annotate).
+/// </summary>
+[ApiController]
+[Route("api/pdf/operations")]
+public class PdfOperationsController(IMediator mediator) : ControllerBase
+{
+    /// <summary>
+    /// Merges multiple PDF files into a single PDF.
+    /// Supports multipart/form-data file upload.
+    /// </summary>
+    /// <param name="files">PDF files to merge (minimum 2 required)</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>Merged PDF file</returns>
+    /// <response code="200">PDFs merged successfully - returns merged PDF</response>
+    /// <response code="400">Invalid input (fewer than 2 files, corrupted PDF)</response>
+    /// <response code="500">Internal server error during PDF processing</response>
+    [HttpPost("merge", Name = "MergeFromFiles")]
+    [Consumes("multipart/form-data")]
+    [ProducesResponseType(typeof(FileContentResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> MergeFromFiles(
+        [FromForm] List<IFormFile> files,
+        CancellationToken cancellationToken)
+    {
+        // Convert IFormFile[] to Stream[] (use OpenReadStream directly - no buffering)
+        var streams = files.Select(f => f.OpenReadStream()).ToList();
+
+        // Send command to MediatR (no page ranges for now - multipart binding is complex)
+        var command = new MergePdfsCommand 
+        { 
+            PdfStreams = streams,
+            PageRanges = null
+        };
+        
+        byte[] mergedPdf = await mediator.Send(command, cancellationToken);
+
+        // Return merged PDF
+        return File(mergedPdf, "application/pdf", "merged.pdf");
+    }
+
+    /// <summary>
+    /// Merges multiple PDF files into a single PDF.
+    /// Supports Base64-encoded PDFs via JSON payload.
+    /// </summary>
+    /// <param name="request">Request containing Base64-encoded PDFs and optional page ranges</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>Merged PDF file</returns>
+    /// <response code="200">PDFs merged successfully - returns merged PDF</response>
+    /// <response code="400">Invalid input (Base64 format error, fewer than 2 files, corrupted PDF, invalid page range)</response>
+    /// <response code="500">Internal server error during PDF processing</response>
+    [HttpPost("merge", Name = "MergeFromBase64")]
+    [Consumes("application/json")]
+    [ProducesResponseType(typeof(FileContentResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> MergeFromBase64(
+        [FromBody] MergePdfsBase64Request request,
+        CancellationToken cancellationToken)
+    {
+        // Convert Base64[] to MemoryStream[]
+        List<Stream> streams = [];
+        try
+        {
+            foreach (var base64Pdf in request.Base64Pdfs)
+            {
+                byte[] pdfBytes = Convert.FromBase64String(base64Pdf);
+                streams.Add(new MemoryStream(pdfBytes));
+            }
+        }
+        catch (FormatException ex)
+        {
+            // Dispose opened streams on error
+            foreach (var stream in streams) stream.Dispose();
+            throw new BadRequestException("Invalid Base64 format: " + ex.Message);
+        }
+
+        var command = new MergePdfsCommand 
+        { 
+            PdfStreams = streams,
+            PageRanges = request.PageRanges
+        };
+        
+        byte[] mergedPdf = await mediator.Send(command, cancellationToken);
+
+        // Cleanup streams (important for MemoryStreams we created)
+        foreach (var stream in streams) stream.Dispose();
+
+        return File(mergedPdf, "application/pdf", "merged.pdf");
+    }
+
+    /// <summary>
+    /// Adds an annotation to a PDF document.
+    /// Supports multipart/form-data file upload.
+    /// </summary>
+    /// <param name="request">Multipart form data containing PDF file and annotation parameters</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>Annotated PDF file</returns>
+    /// <response code="200">Annotation added successfully - returns annotated PDF</response>
+    /// <response code="400">Invalid input (invalid page number, missing required parameters)</response>
+    /// <response code="500">Internal server error during PDF processing</response>
+    [HttpPost("annotate", Name = "AnnotateFromFile")]
+    [Consumes("multipart/form-data")]
+    [ProducesResponseType(typeof(FileContentResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> AnnotateFromFile(
+        [FromForm] AddAnnotationMultipartRequest request,
+        CancellationToken cancellationToken)
+    {
+        // Calculate X2, Y2 from Width/Height if provided
+        double x2 = request.X2 ?? request.X1 + (request.Width ?? throw new BadRequestException("Either X2 or Width must be provided"));
+        double y2 = request.Y2 ?? request.Y1 + (request.Height ?? throw new BadRequestException("Either Y2 or Height must be provided"));
+
+        var command = new AddAnnotationCommand
+        {
+            PdfStream = request.File.OpenReadStream(),
+            AnnotationType = request.AnnotationType,
+            PageNumber = request.PageNumber,
+            Rectangle = (request.X1, request.Y1, x2, y2),
+            Content = request.Content,
+            Author = request.Author,
+            Color = request.Color,
+            TextMarkupStyle = request.TextMarkupStyle,
+            Origin = request.Origin
+        };
+
+        byte[] annotatedPdf = await mediator.Send(command, cancellationToken);
+
+        return File(annotatedPdf, "application/pdf", "annotated.pdf");
+    }
+
+    /// <summary>
+    /// Adds an annotation to a PDF document.
+    /// Supports Base64-encoded PDF via JSON payload.
+    /// </summary>
+    /// <param name="command">Command containing all annotation parameters (including Base64 PDF)</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>Annotated PDF file</returns>
+    /// <response code="200">Annotation added successfully - returns annotated PDF</response>
+    /// <response code="400">Invalid input (Base64 format error, invalid page number, missing required parameters)</response>
+    /// <response code="500">Internal server error during PDF processing</response>
+    [HttpPost("annotate", Name = "AnnotateFromBase64")]
+    [Consumes("application/json")]
+    [ProducesResponseType(typeof(FileContentResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> AnnotateFromBase64(
+        [FromBody] AddAnnotationBase64Request command,
+        CancellationToken cancellationToken)
+    {
+        // Convert Base64 to MemoryStream
+        Stream pdfStream;
+        try
+        {
+            byte[] pdfBytes = Convert.FromBase64String(command.Base64Pdf);
+            pdfStream = new MemoryStream(pdfBytes);
+        }
+        catch (FormatException ex)
+        {
+            throw new BadRequestException("Invalid Base64 format: " + ex.Message);
+        }
+
+        // Calculate X2, Y2 from Width/Height if provided
+        double x2 = command.X2 ?? command.X1 + (command.Width ?? throw new BadRequestException("Either X2 or Width must be provided"));
+        double y2 = command.Y2 ?? command.Y1 + (command.Height ?? throw new BadRequestException("Either Y2 or Height must be provided"));
+
+        var annotationCommand = new AddAnnotationCommand
+        {
+            PdfStream = pdfStream,
+            AnnotationType = command.AnnotationType,
+            PageNumber = command.PageNumber,
+            Rectangle = (command.X1, command.Y1, x2, y2),
+            Content = command.Content,
+            Author = command.Author,
+            Color = command.Color,
+            TextMarkupStyle = command.TextMarkupStyle,
+            Origin = command.Origin
+        };
+
+        byte[] annotatedPdf = await mediator.Send(annotationCommand, cancellationToken);
+
+        // Cleanup stream
+        pdfStream.Dispose();
+
+        return File(annotatedPdf, "application/pdf", "annotated.pdf");
+    }
+
+    /// <summary>
+    /// Adds a stamp (text, image, or predefined) to PDF pages.
+    /// Supports multipart/form-data file upload.
+    /// </summary>
+    /// <param name="request">Multipart form data containing PDF file and stamp parameters</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>Stamped PDF file</returns>
+    /// <response code="200">Stamp added successfully - returns stamped PDF</response>
+    /// <response code="400">Invalid input (invalid page number, missing required parameters, invalid image format)</response>
+    /// <response code="500">Internal server error during PDF processing</response>
+    [HttpPost("stamp", Name = "AddStampFromFile")]
+    [Consumes("multipart/form-data")]
+    [ProducesResponseType(typeof(FileContentResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> AddStampFromFile(
+        [FromForm] AddStampMultipartRequest request,
+        CancellationToken cancellationToken)
+    {
+        // Convert ImageFile to byte[] if provided
+        byte[]? imageBytes = null;
+        if (request.ImageFile != null)
+        {
+            using var ms = new MemoryStream();
+            await request.ImageFile.CopyToAsync(ms, cancellationToken);
+            imageBytes = ms.ToArray();
+        }
+
+        var command = new AddStampCommand
+        {
+            PdfStream = request.File.OpenReadStream(),
+            StampType = request.StampType,
+            PageNumbers = request.PageNumbers,
+            Position = (request.X, request.Y),
+            Size = request.Width.HasValue && request.Height.HasValue 
+                ? (request.Width.Value, request.Height.Value) 
+                : null,
+            Origin = request.Origin,
+            Text = request.Text,
+            FontName = request.FontName,
+            FontSize = request.FontSize,
+            Color = request.Color,
+            Opacity = request.Opacity,
+            Rotation = request.Rotation,
+            Placement = request.Placement,
+            ImageBytes = imageBytes,
+            PredefinedType = request.PredefinedType
+        };
+
+        byte[] stampedPdf = await mediator.Send(command, cancellationToken);
+
+        return File(stampedPdf, "application/pdf", "stamped.pdf");
+    }
+
+    /// <summary>
+    /// Adds a stamp (text, image, or predefined) to PDF pages.
+    /// Supports Base64-encoded PDF and image via JSON payload.
+    /// </summary>
+    /// <param name="request">Request containing Base64-encoded PDF, stamp parameters, and optional Base64 image</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>Stamped PDF file</returns>
+    /// <response code="200">Stamp added successfully - returns stamped PDF</response>
+    /// <response code="400">Invalid input (Base64 format error, invalid page number, missing required parameters)</response>
+    /// <response code="500">Internal server error during PDF processing</response>
+    [HttpPost("stamp", Name = "AddStampFromBase64")]
+    [Consumes("application/json")]
+    [ProducesResponseType(typeof(FileContentResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> AddStampFromBase64(
+        [FromBody] AddStampBase64Request request,
+        CancellationToken cancellationToken)
+    {
+        // Convert Base64 PDF to MemoryStream
+        Stream pdfStream;
+        try
+        {
+            byte[] pdfBytes = Convert.FromBase64String(request.Base64Pdf);
+            pdfStream = new MemoryStream(pdfBytes);
+        }
+        catch (FormatException ex)
+        {
+            throw new BadRequestException("Invalid Base64 PDF format: " + ex.Message);
+        }
+
+        // Convert Base64 image to byte[] if provided
+        byte[]? imageBytes = null;
+        if (!string.IsNullOrWhiteSpace(request.Base64Image))
+        {
+            try
+            {
+                imageBytes = Convert.FromBase64String(request.Base64Image);
+            }
+            catch (FormatException ex)
+            {
+                pdfStream.Dispose();
+                throw new BadRequestException("Invalid Base64 image format: " + ex.Message);
+            }
+        }
+
+        var command = new AddStampCommand
+        {
+            PdfStream = pdfStream,
+            StampType = request.StampType,
+            PageNumbers = request.PageNumbers,
+            Position = (request.X, request.Y),
+            Size = request.Width.HasValue && request.Height.HasValue 
+                ? (request.Width.Value, request.Height.Value) 
+                : null,
+            Origin = request.Origin,
+            Text = request.Text,
+            FontName = request.FontName,
+            FontSize = request.FontSize,
+            Color = request.Color,
+            Opacity = request.Opacity,
+            Rotation = request.Rotation,
+            Placement = request.Placement,
+            ImageBytes = imageBytes,
+            PredefinedType = request.PredefinedType
+        };
+
+        byte[] stampedPdf = await mediator.Send(command, cancellationToken);
+
+        // Cleanup stream
+        pdfStream.Dispose();
+
+        return File(stampedPdf, "application/pdf", "stamped.pdf");
+    }
+}
+
+/// <summary>
+/// Request DTO for multipart/form-data annotation operation
+/// </summary>
+public class AddAnnotationMultipartRequest
+{
+    /// <summary>
+    /// PDF file to annotate
+    /// </summary>
+    public required IFormFile File { get; set; }
+
+    /// <summary>
+    /// Type of annotation (TextMarkup, FreeText, StickyNote, Circle, Square)
+    /// </summary>
+    public required AnnotationType AnnotationType { get; set; }
+
+    /// <summary>
+    /// Target page number (1-indexed)
+    /// </summary>
+    public required int PageNumber { get; set; }
+
+    /// <summary>
+    /// Rectangle X1 coordinate (left)
+    /// </summary>
+    public required double X1 { get; set; }
+
+    /// <summary>
+    /// Rectangle Y1 coordinate (top or bottom depending on Origin)
+    /// </summary>
+    public required double Y1 { get; set; }
+
+    /// <summary>
+    /// Rectangle X2 coordinate (right). Optional if Width is provided.
+    /// </summary>
+    public double? X2 { get; set; }
+
+    /// <summary>
+    /// Rectangle Y2 coordinate (bottom or top depending on Origin). Optional if Height is provided.
+    /// </summary>
+    public double? Y2 { get; set; }
+
+    /// <summary>
+    /// Rectangle width. Alternative to X2 (X2 = X1 + Width). Optional if X2 is provided.
+    /// </summary>
+    public double? Width { get; set; }
+
+    /// <summary>
+    /// Rectangle height. Alternative to Y2 (Y2 = Y1 + Height). Optional if Y2 is provided.
+    /// </summary>
+    public double? Height { get; set; }
+
+    /// <summary>
+    /// Annotation content (required for FreeText/StickyNote)
+    /// </summary>
+    public string? Content { get; set; }
+
+    /// <summary>
+    /// Author name (optional)
+    /// </summary>
+    public string? Author { get; set; }
+
+    /// <summary>
+    /// Hex color (6 digits, e.g., "FF0000" for red)
+    /// </summary>
+    public string? Color { get; set; }
+
+    /// <summary>
+    /// Markup style (Highlight/Underline/Strikeout, required for TextMarkup)
+    /// </summary>
+    public TextMarkupStyle? TextMarkupStyle { get; set; }
+
+    /// <summary>
+    /// Coordinate origin (BottomLeft = PDF native, TopLeft = UI-friendly). Default: BottomLeft
+    /// </summary>
+    public AnnotationOrigin Origin { get; set; } = AnnotationOrigin.BottomLeft;
+}
+
+/// <summary>
+/// Request DTO for multipart/form-data stamp operation
+/// </summary>
+public class AddStampMultipartRequest
+{
+    /// <summary>
+    /// PDF file to stamp
+    /// </summary>
+    public required IFormFile File { get; set; }
+
+    /// <summary>
+    /// Type of stamp (Text, Image, or Predefined)
+    /// </summary>
+    public required StampType StampType { get; set; }
+
+    /// <summary>
+    /// Target page numbers (1-indexed). Null or empty = all pages.
+    /// </summary>
+    /// <example>[1, 3, 5]</example>
+    public int[]? PageNumbers { get; set; }
+
+    /// <summary>
+    /// Stamp position X coordinate
+    /// </summary>
+    /// <example>100.0</example>
+    public required double X { get; set; }
+
+    /// <summary>
+    /// Stamp position Y coordinate
+    /// </summary>
+    /// <example>100.0</example>
+    public required double Y { get; set; }
+
+    /// <summary>
+    /// Stamp width (optional, auto-size for images if not specified)
+    /// </summary>
+    /// <example>200.0</example>
+    public double? Width { get; set; }
+
+    /// <summary>
+    /// Stamp height (optional, auto-size for images if not specified)
+    /// </summary>
+    /// <example>50.0</example>
+    public double? Height { get; set; }
+
+    /// <summary>
+    /// Coordinate origin (BottomLeft = PDF native, TopLeft = UI-friendly). Default: BottomLeft
+    /// </summary>
+    /// <example>BottomLeft</example>
+    public AnnotationOrigin Origin { get; set; } = AnnotationOrigin.BottomLeft;
+
+    /// <summary>
+    /// Text content (required for Text stamps)
+    /// </summary>
+    /// <example>"CONFIDENTIAL"</example>
+    public string? Text { get; set; }
+
+    /// <summary>
+    /// Font name (default: Arial)
+    /// </summary>
+    /// <example>"Arial"</example>
+    public string? FontName { get; set; }
+
+    /// <summary>
+    /// Font size in points (default: 12)
+    /// </summary>
+    /// <example>24.0</example>
+    public double? FontSize { get; set; }
+
+    /// <summary>
+    /// Hex color (6 digits, e.g., "FF0000" for red, default: "000000")
+    /// </summary>
+    /// <example>"FF0000"</example>
+    public string? Color { get; set; }
+
+    /// <summary>
+    /// Opacity (0.0 = transparent, 1.0 = opaque, default: 0.5)
+    /// </summary>
+    /// <example>0.5</example>
+    public double? Opacity { get; set; }
+
+    /// <summary>
+    /// Rotation angle in degrees (0-360, default: 0)
+    /// </summary>
+    /// <example>45.0</example>
+    public double? Rotation { get; set; }
+
+    /// <summary>
+    /// Stamp placement (Foreground = on top, Background = watermark effect, default: Foreground)
+    /// </summary>
+    /// <example>Foreground</example>
+    public StampPlacement Placement { get; set; } = StampPlacement.Foreground;
+
+    /// <summary>
+    /// Image file (required for Image stamps, PNG/JPEG)
+    /// </summary>
+    public IFormFile? ImageFile { get; set; }
+
+    /// <summary>
+    /// Predefined stamp type (required for Predefined stamps)
+    /// </summary>
+    /// <example>Confidential</example>
+    public PredefinedStampType? PredefinedType { get; set; }
+}

DocumentService.API/Controllers/PdfValidationController.cs

@@ -0,0 +1,170 @@
+using DocumentService.Application.Common.DTOs;
+using DocumentService.Application.ValidatePdf.Queries;
+using DocumentService.Application.ValidatePdfA.Queries;
+using DocumentService.Application.Common.DTOs.Requests;
+using DocumentService.Domain.Common.Exceptions;
+using MediatR;
+using Microsoft.AspNetCore.Mvc;
+
+namespace DocumentService.API.Controllers;
+
+/// <summary>
+/// PDF validation operations
+/// </summary>
+[ApiController]
+[Route("api/pdf/validation")]
+[Produces("application/json")]
+public class PdfValidationController(IMediator Mediator) : ControllerBase
+{
+    /// <summary>
+    /// Validates a PDF document and returns metadata (multipart/form-data)
+    /// </summary>
+    /// <param name="file">PDF file to validate</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>PDF metadata (page count, file size, PDF version, attachments)</returns>
+    /// <response code="200">PDF is valid, metadata returned</response>
+    /// <response code="400">Invalid PDF or file format</response>
+    /// <response code="500">Internal server error during validation</response>
+    [HttpPost("validate")]
+    [Consumes("multipart/form-data")]
+    [ProducesResponseType(typeof(PdfValidationResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> ValidateFromFile(
+        IFormFile file,
+        CancellationToken cancellationToken)
+    {
+        if (file == null || file.Length == 0)
+        {
+            return BadRequest(new ProblemDetails
+            {
+                Title = "Invalid file",
+                Detail = "File is required and cannot be empty",
+                Status = StatusCodes.Status400BadRequest
+            });
+        }
+
+        // Use IFormFile stream directly (no intermediate byte[] conversion)
+        using var pdfStream = file.OpenReadStream();
+        
+        // Direct pass-through to MediatR
+        var query = new ValidatePdfQuery { PdfStream = pdfStream };
+        var result = await Mediator.Send(query, cancellationToken);
+        
+        return Ok(result);
+    }
+
+    /// <summary>
+    /// Validates a PDF document and returns metadata (Base64 JSON)
+    /// </summary>
+    /// <param name="request">Request containing Base64-encoded PDF</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>PDF metadata (page count, file size, PDF version, attachments)</returns>
+    /// <response code="200">PDF is valid, metadata returned</response>
+    /// <response code="400">Invalid PDF or Base64 format</response>
+    /// <response code="500">Internal server error during validation</response>
+    [HttpPost("validate")]
+    [Consumes("application/json")]
+    [ProducesResponseType(typeof(PdfValidationResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> ValidateFromBase64(
+        [FromBody] ValidatePdfBase64Request request,
+        CancellationToken cancellationToken)
+    {
+        // Convert Base64 to stream (wrap in try-catch to throw BadRequestException)
+        byte[] pdfBytes;
+        try
+        {
+            pdfBytes = Convert.FromBase64String(request.Base64Pdf);
+        }
+        catch (FormatException ex)
+        {
+            throw new BadRequestException("Invalid Base64 format: " + ex.Message);
+        }
+        
+        using var pdfStream = new MemoryStream(pdfBytes);
+        
+        // Direct pass-through to MediatR
+        var query = new ValidatePdfQuery { PdfStream = pdfStream };
+        var result = await Mediator.Send(query, cancellationToken);
+        
+        return Ok(result);
+    }
+
+    /// <summary>
+    /// Validates a PDF/A document and checks conformance level (multipart/form-data)
+    /// </summary>
+    /// <param name="file">PDF file to validate</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>PDF/A metadata (conformance level, errors, warnings)</returns>
+    /// <response code="200">PDF/A validation completed, results returned</response>
+    /// <response code="400">Invalid PDF or file format</response>
+    /// <response code="500">Internal server error during validation</response>
+    [HttpPost("validate-pdfa")]
+    [Consumes("multipart/form-data")]
+    [ProducesResponseType(typeof(PdfAValidationResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> ValidatePdfAFromFile(
+        IFormFile file,
+        CancellationToken cancellationToken)
+    {
+        if (file == null || file.Length == 0)
+        {
+            return BadRequest(new ProblemDetails
+            {
+                Title = "Invalid file",
+                Detail = "File is required and cannot be empty",
+                Status = StatusCodes.Status400BadRequest
+            });
+        }
+
+        // Use IFormFile stream directly (no intermediate byte[] conversion)
+        using var pdfStream = file.OpenReadStream();
+        
+        // Direct pass-through to MediatR
+        var query = new ValidatePdfAQuery { PdfStream = pdfStream };
+        var result = await Mediator.Send(query, cancellationToken);
+        
+        return Ok(result);
+    }
+
+    /// <summary>
+    /// Validates a PDF/A document and checks conformance level (Base64 JSON)
+    /// </summary>
+    /// <param name="request">Request containing Base64-encoded PDF</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>PDF/A metadata (conformance level, errors, warnings)</returns>
+    /// <response code="200">PDF/A validation completed, results returned</response>
+    /// <response code="400">Invalid PDF or Base64 format</response>
+    /// <response code="500">Internal server error during validation</response>
+    [HttpPost("validate-pdfa")]
+    [Consumes("application/json")]
+    [ProducesResponseType(typeof(PdfAValidationResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> ValidatePdfAFromBase64(
+        [FromBody] ValidatePdfABase64Request request,
+        CancellationToken cancellationToken)
+    {
+        // Convert Base64 to stream (wrap in try-catch to throw BadRequestException)
+        byte[] pdfBytes;
+        try
+        {
+            pdfBytes = Convert.FromBase64String(request.Base64Pdf);
+        }
+        catch (FormatException ex)
+        {
+            throw new BadRequestException("Invalid Base64 format: " + ex.Message);
+        }
+        
+        using var pdfStream = new MemoryStream(pdfBytes);
+        
+        // Direct pass-through to MediatR
+        var query = new ValidatePdfAQuery { PdfStream = pdfStream };
+        var result = await Mediator.Send(query, cancellationToken);
+        
+        return Ok(result);
+    }
+}

DocumentService.API/Controllers/SwissQrCodeController.cs

@@ -0,0 +1,103 @@
+using DocumentService.Application.Common.DTOs;
+using DocumentService.Application.Common.DTOs.Requests;
+using DocumentService.Application.SwissQrCode.Queries;
+using DocumentService.Domain.Common.Exceptions;
+using MediatR;
+using Microsoft.AspNetCore.Mvc;
+
+namespace DocumentService.API.Controllers;
+
+/// <summary>
+/// Swiss QR Code extraction operations
+/// </summary>
+[ApiController]
+[Route("api/pdf/qr-code")]
+[Produces("application/json")]
+public class SwissQrCodeController(IMediator Mediator) : ControllerBase
+{
+    /// <summary>
+    /// Extracts Swiss QR Code from the last page of a PDF document (multipart/form-data)
+    /// </summary>
+    /// <param name="file">PDF file containing Swiss QR Code</param>
+    /// <param name="raw">If true, returns raw QR text lines instead of parsed Bill object</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>Swiss QR Code data (IBAN, amount, creditor, debtor, reference, etc.)</returns>
+    /// <response code="200">Swiss QR Code extracted successfully</response>
+    /// <response code="400">Invalid PDF or file format</response>
+    /// <response code="404">No Swiss QR Code found on the last page</response>
+    /// <response code="500">Internal server error during extraction</response>
+    [HttpPost("extract-swiss")]
+    [Consumes("multipart/form-data")]
+    [ProducesResponseType(typeof(SwissQrCodeExtractionResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status404NotFound)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> ExtractFromFile(
+        IFormFile file,
+        [FromQuery] bool raw = false,
+        CancellationToken cancellationToken = default)
+    {
+        if (file.Length == 0)
+            return BadRequest(new ProblemDetails
+            {
+                Title = "Invalid file",
+                Detail = "File is required and cannot be empty",
+                Status = StatusCodes.Status400BadRequest
+            });
+
+        // Use IFormFile stream directly (no intermediate byte[] conversion)
+        using var pdfStream = file.OpenReadStream();
+
+        // Direct pass-through to MediatR
+        var query = new ExtractSwissQrCodeQuery 
+        { 
+            PdfStream = pdfStream
+        };
+        var result = await Mediator.Send(query, cancellationToken);
+
+        return Ok(raw ? result.RawLines : result.Bill);
+    }
+
+    /// <summary>
+    /// Extracts Swiss QR Code from the last page of a PDF document (Base64 JSON)
+    /// </summary>
+    /// <param name="request">Request containing Base64-encoded PDF</param>
+    /// <param name="raw">If true, returns raw QR text lines instead of parsed Bill object</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>Swiss QR Code data (IBAN, amount, creditor, debtor, reference, etc.)</returns>
+    /// <response code="200">Swiss QR Code extracted successfully</response>
+    /// <response code="400">Invalid PDF or Base64 format</response>
+    /// <response code="404">No Swiss QR Code found on the last page</response>
+    /// <response code="500">Internal server error during extraction</response>
+    [HttpPost("extract-swiss")]
+    [Consumes("application/json")]
+    [ProducesResponseType(typeof(SwissQrCodeExtractionResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status404NotFound)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> ExtractFromBase64(
+        [FromBody] ExtractSwissQrCodeBase64Request request,
+        [FromQuery] bool raw = false,
+        CancellationToken cancellationToken = default)
+    {
+        // Convert Base64 to stream (wrap in try-catch to throw BadRequestException)
+        byte[] pdfBytes;
+        try
+        {
+            pdfBytes = Convert.FromBase64String(request.Base64Pdf);
+        }
+        catch (FormatException ex)
+        {
+            throw new BadRequestException("Invalid Base64 format: " + ex.Message);
+        }
+        
+        using var pdfStream = new MemoryStream(pdfBytes);
+        
+        // Direct pass-through to MediatR
+        var query = new ExtractSwissQrCodeQuery { PdfStream = pdfStream };
+        var result = await Mediator.Send(query, cancellationToken);
+
+        return Ok(raw ? result.RawLines : result.Bill);
+    }
+}
+

DocumentService.API/Controllers/ZugferdController.cs

@@ -0,0 +1,179 @@
+using DocumentService.Application.Common.DTOs;
+using DocumentService.Application.ExtractZugferd;
+using DocumentService.Application.HasZugferd.Queries;
+using DocumentService.Application.Common.DTOs.Requests;
+using DocumentService.Domain.Common.Exceptions;
+using MediatR;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Mvc;
+
+namespace DocumentService.API.Controllers;
+
+/// <summary>
+/// Controller for ZUGFeRD operations (detection, extraction)
+/// </summary>
+[ApiController]
+[Route("api/pdf/zugferd")]
+[Produces("application/json")]
+public class ZugferdController(IMediator mediator) : ControllerBase
+{
+    /// <summary>
+    /// Checks if a PDF contains ZUGFeRD XML attachment.
+    /// Supports multipart/form-data file upload.
+    /// </summary>
+    /// <param name="file">The PDF file to check for ZUGFeRD</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>ZUGFeRD check result with metadata</returns>
+    /// <response code="200">PDF successfully checked - returns ZUGFeRD status</response>
+    /// <response code="400">Invalid input (file missing, not a PDF, or corrupted)</response>
+    /// <response code="500">Internal server error during PDF processing</response>
+    [HttpPost("has-zugferd")]
+    [Consumes("multipart/form-data")]
+    [ProducesResponseType(typeof(ZugferdCheckResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> HasZugferdFromFile(
+        IFormFile file,
+        CancellationToken cancellationToken)
+    {
+        // Use IFormFile stream directly (no intermediate byte[] conversion)
+        using var pdfStream = file.OpenReadStream();
+
+        // Send query to MediatR (ValidationBehavior runs automatically)
+        var query = new HasZugferdQuery { PdfStream = pdfStream };
+        var result = await mediator.Send(query, cancellationToken);
+
+        return Ok(result);
+    }
+
+    /// <summary>
+    /// Checks if a PDF contains ZUGFeRD XML attachment.
+    /// Supports Base64-encoded PDF via JSON payload.
+    /// </summary>
+    /// <param name="request">Request containing Base64-encoded PDF</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>ZUGFeRD check result with metadata</returns>
+    /// <response code="200">PDF successfully checked - returns ZUGFeRD status</response>
+    /// <response code="400">Invalid input (Base64 format error, not a PDF, or corrupted)</response>
+    /// <response code="500">Internal server error during PDF processing</response>
+    [HttpPost("has-zugferd")]
+    [Consumes("application/json")]
+    [ProducesResponseType(typeof(ZugferdCheckResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> HasZugferdFromBase64(
+        [FromBody] HasZugferdRequest request,
+        CancellationToken cancellationToken)
+    {
+        // Convert Base64 to stream (wrap in try-catch to throw BadRequestException)
+        byte[] pdfBytes;
+        try
+        {
+            pdfBytes = Convert.FromBase64String(request.Base64Pdf);
+        }
+        catch (FormatException ex)
+        {
+            throw new BadRequestException("Invalid Base64 format: " + ex.Message);
+        }
+        
+        using var pdfStream = new MemoryStream(pdfBytes);
+        
+        // Send query to MediatR (ValidationBehavior runs automatically)
+        var query = new HasZugferdQuery { PdfStream = pdfStream };
+        var result = await mediator.Send(query, cancellationToken);
+
+        return Ok(result);
+    }
+
+    /// <summary>
+    /// Extracts ZUGFeRD XML from a PDF document.
+    /// Supports multipart/form-data file upload.
+    /// </summary>
+    /// <param name="file">The PDF file to extract ZUGFeRD from</param>
+    /// <param name="asFile">if true, 'file' (returns XML file directly); otherwise output format: 'json' (default, returns metadata + XML content)</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>ZUGFeRD XML content and metadata (JSON) or XML file (application/xml)</returns>
+    /// <response code="200">ZUGFeRD XML extracted successfully</response>
+    /// <response code="400">Invalid input (file missing, not a PDF, or corrupted)</response>
+    /// <response code="404">PDF contains no ZUGFeRD XML</response>
+    /// <response code="500">Internal server error during PDF processing</response>
+    [HttpPost("extract")]
+    [Consumes("multipart/form-data")]
+    [ProducesResponseType(typeof(ZugferdExtractionResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(FileContentResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status404NotFound)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> ExtractZugferdFromFile(
+        IFormFile file,
+        [FromQuery] bool asFile = true,
+        CancellationToken cancellationToken = default)
+    {
+        // Use IFormFile stream directly (no intermediate byte[] conversion)
+        using var pdfStream = file.OpenReadStream();
+
+        // Send command to MediatR
+        var command = new ExtractZugferdCommand { PdfStream = pdfStream };
+        var result = await mediator.Send(command, cancellationToken);
+
+        // Return as file or JSON based on format parameter
+        if (asFile)
+        {
+            byte[] xmlBytes = System.Text.Encoding.UTF8.GetBytes(result.XmlContent);
+            return File(xmlBytes, "application/xml", result.FileName);
+        }
+
+        return Ok(result);
+    }
+
+    /// <summary>
+    /// Extracts ZUGFeRD XML from a PDF document.
+    /// Supports Base64-encoded PDF via JSON payload.
+    /// </summary>
+    /// <param name="request">Request containing Base64-encoded PDF</param>
+    /// <param name="format">Output format: 'json' (default, returns metadata + XML content) or 'file' (returns XML file directly)</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>ZUGFeRD XML content and metadata (JSON) or XML file (application/xml)</returns>
+    /// <response code="200">ZUGFeRD XML extracted successfully</response>
+    /// <response code="400">Invalid input (Base64 format error, not a PDF, or corrupted)</response>
+    /// <response code="404">PDF contains no ZUGFeRD XML</response>
+    /// <response code="500">Internal server error during PDF processing</response>
+    [HttpPost("extract")]
+    [Consumes("application/json")]
+    [ProducesResponseType(typeof(ZugferdExtractionResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(FileContentResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status404NotFound)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> ExtractZugferdFromBase64(
+        [FromBody] ExtractZugferdRequest request,
+        [FromQuery] string format = "json",
+        CancellationToken cancellationToken = default)
+    {
+        // Convert Base64 to stream (wrap in try-catch to throw BadRequestException)
+        byte[] pdfBytes;
+        try
+        {
+            pdfBytes = Convert.FromBase64String(request.Base64Pdf);
+        }
+        catch (FormatException ex)
+        {
+            throw new BadRequestException("Invalid Base64 format: " + ex.Message);
+        }
+        
+        using var pdfStream = new MemoryStream(pdfBytes);
+
+        // Send command to MediatR
+        var command = new ExtractZugferdCommand { PdfStream = pdfStream };
+        var result = await mediator.Send(command, cancellationToken);
+
+        // Return as file or JSON based on format parameter
+        if (format.Equals("file", StringComparison.OrdinalIgnoreCase))
+        {
+            byte[] xmlBytes = System.Text.Encoding.UTF8.GetBytes(result.XmlContent);
+            return File(xmlBytes, "application/xml", result.FileName);
+        }
+
+        return Ok(result);
+    }
+}

DocumentService.API/DocumentService.API.csproj

@@ -0,0 +1,41 @@
+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <GenerateDocumentationFile>true</GenerateDocumentationFile>
+    <PackageId>DocumentOperator.API</PackageId>
+    <Authors>Digital Data GmbH</Authors>
+    <Company>Digital Data GmbH</Company>
+    <Product>DocumentOperator.API</Product>
+    <Version>1.1.0</Version>
+    <FileVersion>1.1.0.0</FileVersion>
+    <AssemblyVersion>1.1.0.0</AssemblyVersion>
+    <InformationalVersion>1.1.0</InformationalVersion>
+    <Copyright>Copyright © 2026 Digital Data GmbH. All rights reserved.</Copyright>
+    <Description>PDF Document Operations REST API - Validation, Swiss QR Code extraction, attachments, merge, annotation, stamp operations powered by DevExpress Office File API</Description>
+    <PackageTags>pdf document operator validation swiss-qr-code annotations stamp devexpress</PackageTags>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Asp.Versioning.Http" Version="8.1.1" />
+    <PackageReference Include="Microsoft.Extensions.Caching.StackExchangeRedis" Version="8.0.28" />
+    <PackageReference Include="Scalar.AspNetCore" Version="1.2.58" />
+    <PackageReference Include="Serilog.AspNetCore" Version="10.0.0" />
+    <PackageReference Include="Serilog.Enrichers.Environment" Version="3.0.1" />
+    <PackageReference Include="Serilog.Sinks.File" Version="7.0.0" />
+    <PackageReference Include="Serilog.Sinks.SQLite" Version="7.0.0" />
+    <PackageReference Include="Serilog.UI" Version="3.2.0" />
+    <PackageReference Include="Serilog.UI.SqliteProvider" Version="1.1.0" />
+    <PackageReference Include="Swashbuckle.AspNetCore" Version="6.6.2" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\DocumentService.Application\DocumentService.Application.csproj" />
+    <ProjectReference Include="..\DocumentService.Client\DocumentService.Client.csproj" />
+    <ProjectReference Include="..\DocumentService.Domain\DocumentService.Domain.csproj" />
+    <ProjectReference Include="..\DocumentService.Infrastructure\DocumentService.Infrastructure.csproj" />
+  </ItemGroup>
+
+</Project>

DocumentService.API/DocumentService.API.http

@@ -0,0 +1,6 @@
+@DocumentService.API_HostAddress = http://localhost:5028
+
+GET {{DocumentService.API_HostAddress}}/weatherforecast/
+Accept: application/json
+
+###

DocumentService.API/Middleware/ExceptionHandlingMiddleware.cs

@@ -0,0 +1,109 @@
+using DocumentService.Domain.Common.Exceptions;
+using FluentValidation;
+using Microsoft.AspNetCore.Mvc;
+using System.Net;
+using System.Text.Json;
+
+namespace DocumentService.API.Middleware;
+
+/// <summary>
+/// Central exception handling middleware
+/// Maps exceptions to HTTP status codes and RFC 7807 Problem Details
+/// </summary>
+/// <remarks>
+/// Initializes a new instance of the <see cref="ExceptionHandlingMiddleware"/> class.
+/// </remarks>
+/// <param name="Next">The next middleware in the pipeline.</param>
+public class ExceptionHandlingMiddleware(RequestDelegate Next)
+{
+    private static readonly JsonSerializerOptions ProbDetailsJsonOpt = new()
+    {
+        PropertyNamingPolicy = JsonNamingPolicy.CamelCase
+    };
+
+    /// <summary>
+    /// Invokes the middleware to handle incoming HTTP requests and catch exceptions.
+    /// </summary>
+    /// <param name="context">The HTTP context for the current request.</param>
+    public async Task InvokeAsync(HttpContext context)
+    {
+        try
+        {
+            await Next(context);
+        }
+        catch (Exception ex)
+        {
+            await HandleExceptionAsync(context, ex);
+        }
+    }
+
+    private static async Task HandleExceptionAsync(HttpContext context, Exception exception)
+    {
+        var (statusCode, problemDetails) = MapExceptionToProblemDetails(exception, context);
+
+        context.Response.StatusCode = (int)statusCode;
+        context.Response.ContentType = "application/problem+json";
+
+        await context.Response.WriteAsync(JsonSerializer.Serialize(problemDetails, ProbDetailsJsonOpt));
+    }
+
+    private static (HttpStatusCode StatusCode, ProblemDetails ProblemDetails) MapExceptionToProblemDetails(
+        Exception exception,
+        HttpContext context)
+    {
+        return exception switch
+        {
+            // FluentValidation (400 Bad Request)
+            ValidationException validationEx => (
+                HttpStatusCode.BadRequest,
+                new ProblemDetails
+                {
+                    Type = "https://datatracker.ietf.org/doc/html/rfc7231#section-6.5.1",
+                    Title = "Validation Error",
+                    Status = (int)HttpStatusCode.BadRequest,
+                    Detail = string.Join("; ", validationEx.Errors.Select(e => e.ErrorMessage)),
+                    Instance = context.Request.Path
+                }
+            ),
+
+            // Bad Request Exception (400 Bad Request)
+            BadRequestException badReqEx => (
+                HttpStatusCode.BadRequest,
+                new ProblemDetails
+                {
+                    Type = "https://datatracker.ietf.org/doc/html/rfc7231#section-6.5.4",
+                    Title = "Bad Request",
+                    Status = (int)HttpStatusCode.BadRequest,
+                    Detail = badReqEx.Message,
+                    Instance = context.Request.Path
+                }
+            ),
+
+            // Not Found Exception (404 Not Found)
+            NotFoundException notFoundEx => (
+                HttpStatusCode.NotFound,
+                new ProblemDetails
+                {
+                    Type = "https://datatracker.ietf.org/doc/html/rfc7231#section-6.5.4",
+                    Title = "Resource Not Found",
+                    Status = (int)HttpStatusCode.NotFound,
+                    Detail = notFoundEx.Message,
+                    Instance = context.Request.Path
+                }
+            ),
+
+            // Generic Exception (500 Internal Server Error)
+            _ => (
+                HttpStatusCode.InternalServerError,
+                new ProblemDetails
+                {
+                    Type = "https://datatracker.ietf.org/doc/html/rfc7231#section-6.6.1",
+                    Title = "Internal Server Error",
+                    Status = (int)HttpStatusCode.InternalServerError,
+                    Detail = "An unexpected error occurred. Please contact support.",
+                    Instance = context.Request.Path
+                }
+            )
+        };
+    }
+}

DocumentService.API/Middleware/RequestLoggingMiddleware.cs

@@ -0,0 +1,9 @@
+namespace DocumentService.API.Middleware
+{
+    /// <summary>
+    /// Placeholder middleware for HTTP request/response logging.
+    /// </summary>
+    public class RequestLoggingMiddleware
+    {
+    }
+}

DocumentService.API/Middleware/TenantResolutionMiddleware.cs

@@ -0,0 +1,9 @@
+namespace DocumentService.API.Middleware
+{
+    /// <summary>
+    /// Placeholder middleware for multi-tenancy resolution via X-API-Key header.
+    /// </summary>
+    public class TenantResolutionMiddleware
+    {
+    }
+}

DocumentService.API/PHASENPLAN.md

@@ -0,0 +1,545 @@
+# ?? DocumentService - Phasenplan (Feature-Driven Development)
+
+> **Stand:** 17.01.2025 | **Aktuell:** Feature 3 - ExtractAttachments ? NEXT | **Projektdauer:** 6 Wochen
+
+---
+
+## ?? Übersicht
+
+| Woche | Features / Concerns | Status | Fortschritt |
+|-------|---------------------|--------|-------------|
+| **W1** | Feature 1: ValidatePDF | ? Abgeschlossen | 100% (Foundation + Application + API + Swagger fertig) |
+| **W1-W2** | Feature 2: ExtractSwissQrCode | ? Abgeschlossen | 100% (Domain + Infrastructure + Application + API + Swagger fertig) |
+| **W2** | Feature 3: ExtractAttachments | ? Nächstes Feature | 0% |
+| **W2** | Feature 4: ApplyStamp | ? Geplant | 0% |
+| **W3** | Feature 5: EmbedCertificate | ? Geplant | 0% |
+| **W3** | Feature 6: ConcatenatePDFs (Async) | ? Geplant | 0% |
+| **W4** | Multi-Tenancy (X-API-Key Header) | ? Geplant | 0% |
+| **W5** | Health Checks + Polly + Logging | ? Geplant | 0% |
+| **W6** | Production Deployment | ? Geplant | 0% |
+
+---
+
+## ?? NEUE VORGEHENSWEISE
+
+**Was hat sich geändert?**
+
+? **Feature-by-Feature Development** statt Layer-by-Layer
+- Jedes Feature wird KOMPLETT umgesetzt (Domain ? Infrastructure ? Application ? API ? Tests ? Swagger)
+- Feature ist erst "DONE" wenn es im Swagger testbar ist
+- Dann nächstes Feature
+
+? **Kleine Schritte** (1 Layer pro Step)
+- Nach jedem Step: ROADMAP + PHASENPLAN aktualisieren
+- Commit nach jedem Step
+- Dann weiter
+
+? **Multi-Tenancy & Cross-Cutting Concerns später**
+- Erst alle synchronen Features (1-4)
+- Dann Multi-Tenancy für ALLE Endpoints
+- Dann Health Checks, Polly, Logging
+
+---
+
+## ?? DETAILLIERTER PLAN
+
+### WOCHE 1 - Feature 1: ValidatePDF | ? ABGESCHLOSSEN - 100%
+
+**Ziel:** POST /api/v1/documents/validate Endpoint im Swagger testbar
+
+#### ? Step 1.0: Foundation (ABGESCHLOSSEN)
+**Dauer:** ~2 Tage
+
+**Was wurde erstellt:**
+- ? Solution Structure (4 Projekte)
+- ? Domain Layer (Exceptions, Enums, Value Objects)
+- ? Infrastructure Layer (DevExpressPdfProcessor.ValidateAsync)
+- ? Tests (DevExpressPdfProcessorTests.cs - 6 Tests)
+- ? Build erfolgreich
+
+---
+
+#### ? Step 1.1: Application Layer (MediatR Setup + ValidatePDF Feature) - **ABGESCHLOSSEN**
+**Dauer:** ~4 Stunden
+
+**Was wurde erstellt:**
+1. **MediatR Setup**
+   - ? `Application/DependencyInjection.cs` (Service Registration)
+   - ? `Application/Common/Behaviors/ValidationBehavior.cs` (FluentValidation Pipeline)
+   - ? `Application/Common/Behaviors/LoggingBehavior.cs` (Logging Pipeline mit ILogger<T>)
+
+2. **ValidatePDF Feature (Vertical Slice)**
+   - ? `Application/Features/Documents/ValidatePdf/ValidatePdfQuery.cs`
+   - ? `Application/Features/Documents/ValidatePdf/ValidatePdfHandler.cs`
+   - ? `Application/Features/Documents/ValidatePdf/ValidatePdfValidator.cs`
+
+3. **DTOs**
+   - ? `Application/Common/DTOs/ValidatePdfRequest.cs`
+   - ? `Application/Common/DTOs/ValidatePdfResponse.cs`
+
+4. **Tests**
+   - ? `Tests/Unit/Application/Features/ValidatePdf/ValidatePdfHandlerTests.cs` (2 Tests)
+
+**Akzeptanzkriterien:**
+- ? Build erfolgreich
+- ? Tests grün (Handler Tests: 2/2 passed)
+- ? MediatR Pipeline funktioniert (Validation + Logging)
+
+---
+
+#### ? Step 1.2: API Layer (Endpoint + Exception Middleware) - **ABGESCHLOSSEN**
+**Dauer:** ~3 Stunden
+
+**Was wurde erstellt:**
+1. **Exception Middleware**
+   - ? `API/Middleware/ExceptionHandlingMiddleware.cs`
+   - Exception ? HTTP Status Code Mapping (400, 404, 422, 500)
+   - RFC 7807 Problem Details
+
+2. **Minimal API Endpoint**
+   - ? `API/Endpoints/v1/DocumentEndpoints.cs`
+   - POST /api/v1/documents/validate
+
+3. **Infrastructure DI**
+   - ? `Infrastructure/DependencyInjection.cs`
+   - IPdfProcessor ? DevExpressPdfProcessor registriert
+
+4. **Program.cs Updates**
+   - ? Exception Middleware registriert (FIRST in pipeline!)
+   - ? DocumentEndpoints registriert
+   - ? Application + Infrastructure Services registriert
+
+5. **Integration Tests**
+   - ? `Tests/Integration/API/DocumentEndpointsTests.cs` (3 Tests)
+   - ? Test: `POST_ValidatePdf_ValidPdf_Returns200`
+   - ? Test: `POST_ValidatePdf_InvalidBase64_Returns400`
+   - ? Test: `POST_ValidatePdf_EmptyPdf_Returns400`
+
+**Akzeptanzkriterien:**
+- ? Build erfolgreich
+- ? Integration Tests grün (3/3 passed)
+- ? Endpoint gibt korrekte HTTP Status Codes zurück
+
+---
+
+#### ? Step 1.3: Swagger Dokumentation - **ABGESCHLOSSEN**
+**Dauer:** ~1 Stunde
+
+**Was wurde erstellt:**
+1. **Swagger Configuration**
+   - ? `API/Configuration/SwaggerConfiguration.cs`
+   - ? `AddSwaggerDocumentation()` Extension Method
+   - ? XML Comments aktiviert
+
+2. **XML-Dokumentation aktiviert**
+   - ? `API/DocumentService.API.csproj`
+   - ? `<GenerateDocumentationFile>true</GenerateDocumentationFile>`
+
+3. **Endpoint Dokumentation**
+   - ? `API/Endpoints/v1/DocumentEndpoints.cs`
+   - ? XML Comments für `ValidatePdf` Methode
+   - ? Swagger-Annotationen (`.WithSummary()`, `.WithDescription()`, `.Produces<>()`)
+
+4. **DTOs Dokumentation**
+   - ? `Application/Common/DTOs/ValidatePdfRequest.cs` (XML Comments)
+   - ? `Application/Common/DTOs/ValidatePdfResponse.cs` (XML Comments + `FileSizeMB` hinzugefügt)
+
+5. **Program.cs Updates**
+   - ? `builder.Services.AddSwaggerDocumentation()` statt `AddSwaggerGen()`
+   - ? `using DocumentService.API.Configuration;` hinzugefügt
+
+**Akzeptanzkriterien:**
+- ? Build erfolgreich
+- ? Alle Tests grün (11/11)
+- ? XML-Dokumentation wird generiert (`DocumentService.API.xml`)
+- ? Swagger UI zeigt Endpoint `/api/v1/documents/validate` mit Dokumentation
+- ? Request/Response-Schemas sind dokumentiert
+- ? Endpoint ist im Swagger UI testbar
+
+---
+
+#### ? Feature 1 ABGESCHLOSSEN!
+**Gesamtdauer:** ~1 Tag
+
+**Ergebnis:**
+- ? POST /api/v1/documents/validate im Swagger testbar
+- ? Unit Tests + Integration Tests grün (11/11)
+- ? Clean Architecture eingehalten
+- ? TDD angewendet
+- ? Swagger-Dokumentation vollständig
+
+---
+
+### WOCHE 1-2 - Feature 2: ExtractSwissQrCode | ? ABGESCHLOSSEN - 100%
+
+**Dauer:** ~1-2 Tage
+**Status:** ? Abgeschlossen
+
+**Endpoint:** POST /api/v1/documents/extract-swiss-qr-code
+
+**Was wurde gebaut:**
+- Client sendet Referenzen (Array) + PDF (Base64)
+- API extrahiert Swiss QR Code von **letzter Seite**
+- API gibt Referenzen + alle QR Code Felder zurück (Swiss QR Bill Standard 2.0)
+
+**Technologie:**
+- **DevExpress PDF Document API** (PDF-Zugriff, letzte Seite)
+- **ZXing.Net.Bindings.Windows.Compatibility** (QR Code Detection)
+- **Codecrete.SwissQRBill.Generator** (Swiss QR Code Parsing - Standard 2.0)
+- **System.Drawing.Common** (Bitmap Support)
+
+**Steps:**
+- ? Step 2.1: Domain Layer (SwissQrCodeData Value Object) - ABGESCHLOSSEN
+- ? Step 2.2: Infrastructure Layer (ISwissQrCodeProcessor + DevExpressSwissQrCodeProcessor + Library Integration) - ABGESCHLOSSEN
+- ? Step 2.3: Application Layer (ExtractSwissQrCodeQuery + Handler + Validator + DTOs) - ABGESCHLOSSEN
+- ? Step 2.4: API Layer (Endpoint + Exception Mapping + Integration Tests) - ABGESCHLOSSEN
+- ? Step 2.5: Swagger Dokumentation (XML Comments + Examples) - ABGESCHLOSSEN
+
+**Akzeptanzkriterien:**
+- ? QR Code wird von letzter Seite extrahiert
+- ? Alle Swiss QR Bill Felder werden geparst (Standard 2.0)
+- ? Referenzen werden durchgeschliffen (Echo)
+- ? Fehler wenn kein QR Code gefunden (404 Not Found)
+- ? Swagger-testbar
+- ? Tests grün (19/19)
+
+**Ergebnis:**
+- ? POST /api/v1/documents/extract-swiss-qr-code im Swagger testbar
+- ? Nested Response Structure (References + SwissQrCodeData)
+- ? SwissQrCodeNotFoundException wird zu 404 gemappt
+- ? Unit Tests + Integration Tests grün (19/19)
+- ? Clean Architecture eingehalten
+- ? Swagger-Dokumentation vollständig
+
+---
+
+### WOCHE 2 - Features 3 & 4 | ? Geplant - 0%
+
+#### Feature 3: ExtractAttachments (Synchron)
+**Dauer:** ~1 Tag
+**Status:** ? Pending
+
+**Endpoint:** POST /api/v1/documents/extract-attachments
+
+**Steps:**
+- ? Step 3.1: Infrastructure Layer (DevExpressPdfProcessor.ExtractAttachmentsAsync)
+- ? Step 3.2: Application Layer (ExtractAttachmentsCommand + Handler + Validator)
+- ? Step 3.3: API Layer (Endpoint)
+- ? Step 3.4: Swagger Dokumentation
+
+**Akzeptanzkriterien:**
+- ? Endpoint im Swagger testbar
+- ? Tests grün
+
+---
+
+#### Feature 4: ApplyStamp (Synchron)
+**Dauer:** ~1 Tag
+**Status:** ? Pending
+
+**Endpoint:** POST /api/v1/documents/apply-stamp
+
+**Steps:**
+- ? Step 4.1: Infrastructure Layer (DevExpressPdfProcessor.ApplyStampAsync)
+- ? Step 4.2: Application Layer (ApplyStampCommand + Handler + Validator)
+- ? Step 4.3: API Layer (Endpoint)
+- ? Step 4.4: Swagger Dokumentation
+
+**Akzeptanzkriterien:**
+- ? Endpoint im Swagger testbar
+- ? Stamp wird korrekt angewendet
+- ? Tests grün
+
+---
+
+### WOCHE 3 - Features 5 & 6 | ? Geplant - 0%
+
+#### Feature 5: EmbedCertificate (Synchron)
+**Dauer:** ~1 Tag
+**Status:** ? Pending
+
+**Endpoint:** POST /api/v1/documents/embed-certificate
+
+**Steps:**
+- ? Step 5.1: Infrastructure Layer (DevExpressPdfProcessor.EmbedCertificateAsync)
+- ? Step 5.2: Application Layer (EmbedCertificateCommand + Handler + Validator)
+- ? Step 5.3: API Layer (Endpoint)
+- ? Step 5.4: Swagger Dokumentation
+
+**Akzeptanzkriterien:**
+- ? Endpoint im Swagger testbar
+- ? Zertifikat wird korrekt eingebettet
+- ? Tests grün
+
+---
+
+#### Feature 6: ConcatenatePDFs (Asynchron)
+**Dauer:** ~2 Tage
+**Status:** ? Pending
+
+**Endpoints:**
+- POST /api/v1/documents/concatenate (Async, gibt JobId zurück)
+- GET /api/v1/jobs/{jobId} (Job-Status abfragen)
+- GET /api/v1/jobs/{jobId}/download (Ergebnis herunterladen)
+
+**Steps:**
+- ? Step 6.1: Infrastructure Layer (In-Memory Queue + Background Worker)
+- ? Step 6.2: Application Layer (SubmitConcatenateJobCommand + GetJobStatusQuery)
+- ? Step 6.3: API Layer (Async Endpoints)
+- ? Step 6.4: Swagger Dokumentation
+
+**Akzeptanzkriterien:**
+- ? POST /concatenate gibt JobId zurück
+- ? GET /jobs/{jobId} zeigt Status (Pending, Processing, Success, Failed)
+- ? GET /jobs/{jobId}/download gibt PDF zurück
+- ? Background Worker verarbeitet Jobs korrekt
+- ? Tests grün
+
+---
+
+### WOCHE 4 - Multi-Tenancy | ? Geplant - 0%
+
+**Ziel:** X-API-Key Header für ALLE Endpoints
+
+**Was wird gebaut:**
+- EF Core + SQLite (Tenant-Datenbank)
+- Redis Cache (API-Key Lookups - optional)
+- TenantResolutionMiddleware (X-API-Key ? Tenant)
+- BCrypt API-Key Hashing
+- Admin API (Tenant CRUD)
+
+**Steps:**
+
+#### Step MT.1: EF Core Setup
+**Dauer:** ~3 Stunden
+
+**Was wird erstellt:**
+- `Infrastructure/Data/TenantDbContext.cs`
+- `Infrastructure/Data/Entities/Tenant.cs`
+- `Infrastructure/Data/Entities/TenantSettings.cs`
+- EF Core Migration (InitialCreate)
+- SQLite Database erstellen
+
+**Akzeptanzkriterien:**
+- ? Datenbank erstellt
+- ? Tenant-Tabelle existiert
+- ? Build erfolgreich
+
+---
+
+#### Step MT.2: TenantResolutionMiddleware
+**Dauer:** ~2 Stunden
+
+**Was wird erstellt:**
+- `API/Middleware/TenantResolutionMiddleware.cs`
+- `Application/Common/Interfaces/ITenantContext.cs`
+- `Infrastructure/Services/TenantContext.cs`
+
+**Akzeptanzkriterien:**
+- ? X-API-Key Header wird gelesen
+- ? Tenant aus DB geladen
+- ? ITenantContext im Request Scope verfügbar
+- ? Ungültiger API-Key ? HTTP 401
+
+---
+
+#### Step MT.3: Redis Cache Integration (Optional)
+**Dauer:** ~1 Stunde
+
+**Was wird erstellt:**
+- Redis Cache für API-Key Lookups
+- TTL: 1 Stunde
+
+**Akzeptanzkriterien:**
+- ? API-Key Lookup cached (weniger DB-Calls)
+- ? Cache Invalidation funktioniert
+
+---
+
+#### Step MT.4: Admin API (Tenant Management)
+**Dauer:** ~2 Stunden
+
+**Was wird erstellt:**
+- POST /api/v1/admin/tenants (Create Tenant)
+- PUT /api/v1/admin/tenants/{id}/rotate-key (API-Key rotieren)
+- PATCH /api/v1/admin/tenants/{id}/deactivate (Tenant deaktivieren)
+- GET /api/v1/admin/tenants (Liste aller Tenants)
+
+**Akzeptanzkriterien:**
+- ? Endpoints im Swagger testbar
+- ? API-Key wird gehashed (BCrypt)
+- ? Tests grün
+
+---
+
+#### Step MT.5: Alle Endpoints mit X-API-Key absichern
+**Dauer:** ~1 Stunde
+
+**Was wird geändert:**
+- Alle Feature-Endpoints bekommen X-API-Key Header Requirement
+- Swagger zeigt API-Key Security Scheme
+
+**Akzeptanzkriterien:**
+- ? Alle Endpoints erfordern X-API-Key Header
+- ? Swagger zeigt Security Scheme
+- ? Tests aktualisiert (mit API-Key)
+
+---
+
+### WOCHE 5 - Health Checks + Polly + Logging | ? Geplant - 0%
+
+#### Health Checks
+**Dauer:** ~2 Stunden
+
+**Was wird gebaut:**
+- `/health` Endpoint (Liveness/Readiness Probes)
+- DevExpressPdfHealthCheck (Smoke Test)
+- Database Health Check (SQLite)
+- Redis Health Check (optional)
+
+**Akzeptanzkriterien:**
+- ? /health gibt HTTP 200 wenn alles OK
+- ? /health gibt HTTP 503 wenn DevExpress nicht funktioniert
+
+---
+
+#### Polly Resilience
+**Dauer:** ~3 Stunden
+
+**Was wird gebaut:**
+- Retry Policy (3x mit Exponential Backoff)
+- Circuit Breaker (nach 5 Fehlern 30s öffnen)
+- Timeout Policy (30s max)
+
+**Akzeptanzkriterien:**
+- ? DevExpress Calls werden mit Polly gewickelt
+- ? Retry funktioniert bei Transient Errors
+- ? Circuit Breaker öffnet bei vielen Fehlern
+
+---
+
+#### Logging & Monitoring
+**Dauer:** ~3 Stunden
+
+**Was wird gebaut:**
+- CorrelationIdMiddleware (X-Correlation-ID Header)
+- Seq Sink (Log-Browsing UI)
+- File Logging (Production)
+- LoggingBehavior erweitert (Performance-Tracking)
+
+**Akzeptanzkriterien:**
+- ? Correlation IDs in allen Logs
+- ? Seq UI zeigt Logs (Development)
+- ? File Logging funktioniert (Production)
+
+---
+
+### WOCHE 6 - Production Deployment | ? Geplant - 0%
+
+**Ziel:** Service ist produktionsreif
+
+**Was wird gebaut:**
+- appsettings.Production.json (Production Settings)
+- IIS Web.config (Kestrel Settings)
+- SSL/TLS Zertifikat konfigurieren
+- Deployment-Skript (PowerShell)
+
+**Steps:**
+
+#### Deployment Vorbereitung
+**Dauer:** ~4 Stunden
+
+**Was wird erstellt:**
+- `appsettings.Production.json` (Prod-Settings)
+- `Web.config` (IIS Integration)
+- PowerShell Deploy-Skript
+- Dokumentation (README.md)
+
+**Akzeptanzkriterien:**
+- ? Build in Release Mode erfolgreich
+- ? IIS Deployment funktioniert
+- ? HTTPS funktioniert
+
+---
+
+#### Production Testing
+**Dauer:** ~4 Stunden
+
+**Was wird getestet:**
+- Alle Endpoints im Production-Modus
+- Health Checks
+- Multi-Tenancy
+- Performance (Load Testing)
+
+**Akzeptanzkriterien:**
+- ? Alle Features funktionieren in Production
+- ? Health Checks grün
+- ? Performance OK (< 1s Response Time)
+
+---
+
+## ?? FORTSCHRITTS-TRACKING
+
+### Gesamt-Fortschritt
+
+| Kategorie | Status | Fortschritt |
+|-----------|--------|-------------|
+| **Foundation** | ? Abgeschlossen | 100% |
+| **Feature 1** | ? Abgeschlossen | 100% |
+| **Feature 2-5** | ? Pending | 0% |
+| **Multi-Tenancy** | ? Pending | 0% |
+| **Cross-Cutting** | ? Pending | 0% |
+| **Production** | ? Pending | 0% |
+
+---
+
+## ?? NEXT STEPS
+
+### Nächstes Feature
+
+**Feature 3: ExtractAttachments** - **NEXT**
+1. ?? Step 3.1: Domain Layer (Attachment Value Object)
+2. ?? Step 3.2: Infrastructure Layer (IAttachmentProcessor + DevExpressAttachmentProcessor)
+3. ?? Step 3.3: Application Layer (ExtractAttachmentsQuery + Handler + Validator + DTOs)
+4. ?? Step 3.4: API Layer (Endpoint + Integration Tests)
+5. ?? Step 3.5: Swagger Dokumentation
+
+**Erwarteter Zeitaufwand:** ~1 Tag
+
+**Akzeptanzkriterien:**
+- ? POST /api/v1/documents/extract-attachments im Swagger testbar
+- ? Alle Attachments werden extrahiert
+- ? Attachment-Metadaten werden zurückgegeben
+- ? Alle Tests grün
+- ? Clean Architecture eingehalten
+
+---
+
+## ?? UPDATE LOG
+
+| Date | Feature/Step | Changes |
+|------|--------------|---------|
+| 2024-XX-XX | Foundation | Project setup, dependencies, folder structure |
+| 2024-XX-XX | Domain Layer | Exceptions, Enums, Value Objects |
+| 17.01.2025 | Infrastructure | DevExpressPdfProcessor.ValidateAsync implementiert |
+| 17.01.2025 | Tests | DevExpressPdfProcessorTests.cs erstellt (6 Tests) |
+| 17.01.2025 | **PHASENPLAN** | ?? **Komplett umstrukturiert** (Feature-basiert + Datum korrigiert 23.06.2026 ? 17.01.2025) |
+| 17.01.2025 | **Feature 1 - Step 1.1** | ? **ABGESCHLOSSEN** - Application Layer (MediatR, Behaviors, ValidatePDF Feature, DTOs, Tests - 2/2 grün) |
+| 17.01.2025 | **Feature 1 - Step 1.2** | ? **ABGESCHLOSSEN** - API Layer (ExceptionMiddleware, Endpoint, Program.cs, Integration Tests - 3/3 grün) |
+| 17.01.2025 | **Feature 1 - Step 1.3** | ? **ABGESCHLOSSEN** - Swagger Dokumentation (SwaggerConfiguration, XML Comments, Endpoint/DTO-Dokumentation - 11/11 Tests grün) |
+| 17.01.2025 | **Feature 1** | ? **KOMPLETT ABGESCHLOSSEN** - ValidatePDF Feature testbar im Swagger UI! |
+| 17.01.2025 | **Fix: Attachment Detection (Multiple Attachments)** | ? **KORRIGIERT** - ValidatePDF erkennt jetzt auch PDFs mit mehreren Attachments korrekt (globale Suche statt 1000-Zeichen-Limit) - 13/13 Tests grün |
+| 17.01.2025 | **Fix: Attachment Count (6 Attachments)** | ? **KORRIGIERT** - AttachmentCount wird jetzt korrekt gezählt (objectCount statt objectCount/2). PDFs mit 6 Attachments werden korrekt erkannt - 13/13 Tests grün |
+| 17.01.2025 | **PHASENPLAN** | ?? **Feature-Reihenfolge geändert** - Neues Feature 2: ExtractSwissQrCode (Swiss QR Bill Standard 2.0) eingefügt. Alte Features 2-5 werden zu Features 3-6. |
+| 17.01.2025 | **Feature 2 - Step 2.1** | ? **ABGESCHLOSSEN** - Domain Layer (SwissQrCodeData, AddressData, SwissQrCodeNotFoundException) |
+| 17.01.2025 | **Feature 2 - Step 2.2** | ? **ABGESCHLOSSEN** - Infrastructure Layer (ISwissQrCodeProcessor, DevExpressSwissQrCodeProcessor, ZXing + Codecrete Integration) |
+| 17.01.2025 | **Feature 2 - Step 2.3** | ? **ABGESCHLOSSEN** - Application Layer (ExtractSwissQrCodeQuery, Handler, Validator, Request/Response DTOs, Unit Tests) |
+| 17.01.2025 | **Feature 2 - Step 2.4** | ? **ABGESCHLOSSEN** - API Layer (Endpoint, Exception Mapping, Integration Tests - 19/19 Tests grün) |
+| 17.01.2025 | **Feature 2 - Step 2.5** | ? **ABGESCHLOSSEN** - Swagger Dokumentation (XML Comments, Examples, Endpoint Description) |
+| 17.01.2025 | **Feature 2** | ? **KOMPLETT ABGESCHLOSSEN** - ExtractSwissQrCode Feature testbar im Swagger UI! (19/19 Tests grün) |
+
+---
+
+**END OF PHASENPLAN**
+
+*This document is a living document and will be updated after each completed step.*

DocumentService.API/Program.cs

@@ -0,0 +1,147 @@
+using Serilog;
+using Serilog.Ui.Core.Extensions;
+using Serilog.Ui.SqliteDataProvider.Extensions;
+using Serilog.Ui.Web.Extensions;
+using Scalar.AspNetCore;
+using DocumentService.Infrastructure.Configuration;
+using DocumentService.Application;
+using DocumentService.Application.Common.Configuration;
+using DocumentService.Infrastructure;
+using DocumentService.API.Middleware;
+using DocumentService.API.Configuration;
+
+var builder = WebApplication.CreateBuilder(args);
+
+// ========================================
+// 1. Serilog Configuration
+// ========================================
+Log.Logger = new LoggerConfiguration()
+    .ReadFrom.Configuration(builder.Configuration)
+    .Enrich.FromLogContext()
+    .Enrich.WithProperty("Application", "DocumentService")
+    .CreateLogger();
+
+builder.Host.UseSerilog();
+
+Log.Information("Starting DocumentService API...");
+
+try
+{
+    // ========================================
+    // 2. Options Pattern Configuration
+    // ========================================
+    builder.Services.Configure<DocumentServiceSettings>(
+        builder.Configuration.GetSection(DocumentServiceSettings.SectionName));
+
+    builder.Services.Configure<ZugferdSettings>(
+        builder.Configuration.GetSection("ZugferdSettings"));
+
+    builder.Services.Configure<RedisSettings>(
+        builder.Configuration.GetSection(RedisSettings.SectionName));
+
+    builder.Services.Configure<ApiKeySettings>(
+        builder.Configuration.GetSection(ApiKeySettings.SectionName));
+
+    builder.Services.Configure<SwaggerSettings>(
+        builder.Configuration.GetSection(SwaggerSettings.SectionName));
+
+    // ========================================
+    // 3. Services (Clean Architecture Layers)
+    // ========================================
+    builder.Services.AddApplication(builder.Configuration);      // Application Layer (MediatR, FluentValidation, Behaviors)
+    builder.Services.AddInfrastructure();   // Infrastructure Layer (DevExpress, Services)
+
+    builder.Services.AddControllers();      // Controllers (Controller-based API)
+    builder.Services.AddEndpointsApiExplorer();
+    builder.Services.AddSwaggerDocumentation(builder.Configuration);
+
+    // ========================================
+    // 4. Serilog.UI Configuration
+    // ========================================
+    var logDirectory = builder.Configuration.GetValue<string>("Application:LogDirectory")
+        ?? throw new InvalidOperationException("Application:LogDirectory not found in configuration.");
+    var sqliteDbPath = Path.Combine(logDirectory, "logs.db");
+
+    builder.Services.AddSerilogUi(logUIOpt =>
+    {
+        logUIOpt.UseSqliteServer(dbOpt =>
+        {
+            dbOpt.WithConnectionString($"Data Source={sqliteDbPath}");
+            dbOpt.WithTable("Logs");
+        });
+    });
+
+    // ========================================
+    // 5. Build App
+    // ========================================
+    var app = builder.Build();
+
+    // ========================================
+    // 5. Middleware Pipeline (Order matters!)
+    // ========================================
+
+    // Exception Handling FIRST (catches all exceptions from subsequent middleware)
+    app.UseMiddleware<ExceptionHandlingMiddleware>();
+
+    // ========================================
+    // Swagger/OpenAPI (Conditional based on settings)
+    // ========================================
+    var swaggerSettings = builder.Configuration.GetSection(SwaggerSettings.SectionName).Get<SwaggerSettings>()
+        ?? new SwaggerSettings();
+
+    if (app.Environment.IsDevelopment() || swaggerSettings.EnableInProduction)
+    {
+        app.UseSwagger();
+        
+        // Swagger UI (classic)
+        app.UseSwaggerUI(options =>
+        {
+            options.SwaggerEndpoint($"/swagger/{swaggerSettings.Version}/swagger.json", 
+                $"{swaggerSettings.Title} {swaggerSettings.Version}");
+            options.RoutePrefix = "swagger"; // /swagger
+        });
+
+        // Scalar UI (modern alternative)
+        app.MapScalarApiReference(options =>
+        {
+            options
+                .WithTitle(swaggerSettings.Title)
+                .WithTheme(ScalarTheme.DeepSpace)
+                .WithDefaultHttpClient(ScalarTarget.CSharp, ScalarClient.HttpClient);
+        });
+    }
+
+    app.UseSerilogRequestLogging(); // Log HTTP Requests
+
+    app.UseHttpsRedirection();
+
+    // ========================================
+    // 6. Serilog.UI Dashboard
+    // ========================================
+    app.UseSerilogUi(); // Accessible at /serilog-ui
+
+    // ========================================
+    // 7. Endpoints (Controller-based API)
+    // ========================================
+    app.MapControllers(); // Maps all [ApiController] controllers
+
+    Log.Information("DocumentService API started successfully");
+
+    app.Run();
+}
+catch (Exception ex)
+{
+    Log.Fatal(ex, "Application startup failed");
+    throw;
+}
+finally
+{
+    Log.CloseAndFlush();
+}
+
+// Make Program class accessible for Integration Tests
+/// <summary>
+/// Entry point class for the DocumentService API.
+/// Made partial and public for integration test access.
+/// </summary>
+public partial class Program { }

DocumentService.API/Properties/PublishProfiles/IISProfile.pubxml

@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- https://go.microsoft.com/fwlink/?LinkID=208121. -->
+<Project>
+	<PropertyGroup>
+		<WebPublishMethod>Package</WebPublishMethod>
+		<LastUsedBuildConfiguration>Release</LastUsedBuildConfiguration>
+		<LastUsedPlatform>Any CPU</LastUsedPlatform>
+		<SiteUrlToLaunchAfterPublish />
+		<LaunchSiteAfterPublish>true</LaunchSiteAfterPublish>
+		<ExcludeApp_Data>false</ExcludeApp_Data>
+		<ProjectGuid>c60bc965-d293-ea64-b153-1941f0648df4</ProjectGuid>
+		<DesktopBuildPackageLocation>M:\App&amp;Service\0 DD - Smart UP\DocumentService\PreRelease\API\net8\$(Version)\DocumentService.API.zip</DesktopBuildPackageLocation>
+		<PackageAsSingleFile>true</PackageAsSingleFile>
+		<DeployIisAppPath>DocumentService.API</DeployIisAppPath>
+		<_TargetId>IISWebDeployPackage</_TargetId>
+		<TargetFramework>net8.0</TargetFramework>
+	</PropertyGroup>
+</Project>

DocumentService.API/README.md

@@ -0,0 +1,387 @@
+# DocumentService API - Manual Testing Guide
+
+This guide contains manual test scenarios for validating the DocumentService API endpoints using Swagger UI or tools like Postman.
+
+---
+
+## Prerequisites
+
+1. **Start the API:**
+   ```powershell
+   dotnet run --project DocumentService.API
+   ```
+   Default URL: `https://localhost:5001` (check console output for actual port)
+
+2. **Open Swagger UI:**
+   Navigate to `https://localhost:<port>/swagger`
+
+3. **Test PDFs:**
+   - Use PDFs from `fake-pdf/` folder (form.pdf, multi-page.pdf, one-page.pdf, with-image.pdf)
+   - Or use your own PDF files
+
+---
+
+## Feature 1: Basic PDF Validation
+
+### Endpoint: `POST /api/pdf/validation/validate`
+
+#### Test Case 1.1: Valid PDF (Multipart Upload)
+**Objective:** Verify basic PDF validation works with file upload
+
+**Steps:**
+1. Open Swagger UI → `/api/pdf/validation/validate`
+2. Click "Try it out"
+3. Select **multipart/form-data** from dropdown
+4. Click "Choose File" and select `fake-pdf/one-page.pdf`
+5. Click "Execute"
+
+**Expected Result:**
+- **Status Code:** 200 OK
+- **Response Body:**
+  ```json
+  {
+    "pageCount": 1,
+    "fileSizeBytes": 7168,
+    "fileSizeMB": 0.01,
+    "pdfVersion": "1.4",
+    "hasAttachments": false,
+    "attachmentCount": 0
+  }
+  ```
+
+---
+
+#### Test Case 1.2: Valid PDF (Base64 JSON)
+**Objective:** Verify Base64 input works
+
+**Steps:**
+1. Convert a PDF to Base64:
+   ```powershell
+   $bytes = [System.IO.File]::ReadAllBytes("fake-pdf/one-page.pdf")
+   $base64 = [Convert]::ToBase64String($bytes)
+   Write-Output $base64
+   ```
+2. Open Swagger UI → `/api/pdf/validation/validate`
+3. Click "Try it out"
+4. Select **application/json** from dropdown
+5. Paste into Request Body:
+   ```json
+   {
+     "base64Pdf": "<paste-your-base64-here>"
+   }
+   ```
+6. Click "Execute"
+
+**Expected Result:**
+- **Status Code:** 200 OK
+- Same response as Test 1.1
+
+---
+
+#### Test Case 1.3: Invalid Base64 String
+**Objective:** Verify validation rejects malformed Base64
+
+**Steps:**
+1. Open Swagger UI → `/api/pdf/validation/validate`
+2. Select **application/json**
+3. Paste into Request Body:
+   ```json
+   {
+     "base64Pdf": "invalid-base64!!!"
+   }
+   ```
+4. Click "Execute"
+
+**Expected Result:**
+- **Status Code:** 400 Bad Request
+- **Error Message:** Contains "Base64"
+
+---
+
+#### Test Case 1.4: Empty File Upload
+**Objective:** Verify empty files are rejected
+
+**Steps:**
+1. Create an empty file (`empty.pdf`)
+2. Upload via multipart/form-data
+
+**Expected Result:**
+- **Status Code:** 400 Bad Request
+- **Error Message:** Contains "cannot be empty"
+
+---
+
+#### Test Case 1.5: Large Multi-Page PDF
+**Objective:** Verify handling of larger PDFs
+
+**Steps:**
+1. Upload `fake-pdf/multi-page.pdf` (49 KB)
+
+**Expected Result:**
+- **Status Code:** 200 OK
+- **Response:**
+  ```json
+  {
+    "pageCount": 3,
+    "fileSizeBytes": 49152,
+    "fileSizeMB": 0.05,
+    "pdfVersion": "1.7",
+    "hasAttachments": false,
+    "attachmentCount": 0
+  }
+  ```
+
+---
+
+#### Test Case 1.6: PDF with Images
+**Objective:** Verify image-heavy PDFs are processed
+
+**Steps:**
+1. Upload `fake-pdf/with-image.pdf` (256 KB)
+
+**Expected Result:**
+- **Status Code:** 200 OK
+- **Response:**
+  ```json
+  {
+    "pageCount": 1,
+    "fileSizeBytes": 262144,
+    "fileSizeMB": 0.25,
+    "pdfVersion": "1.6",
+    "hasAttachments": false,
+    "attachmentCount": 0
+  }
+  ```
+
+---
+
+## Feature 3: PDF/A Validation
+
+### Endpoint: `POST /api/pdf/validation/validate-pdfa`
+
+#### Test Case 3.1: PDF/A Compliant Document (Multipart)
+**Objective:** Verify PDF/A validation detects conformance
+
+**Steps:**
+1. Open Swagger UI → `/api/pdf/validation/validate-pdfa`
+2. Select **multipart/form-data**
+3. Upload a PDF/A-compliant PDF (if available)
+4. Click "Execute"
+
+**Expected Result (if PDF/A compliant):**
+- **Status Code:** 200 OK
+- **Response:**
+  ```json
+  {
+    "isValid": true,
+    "pdfVersion": "1.7",
+    "pageCount": 1,
+    "fileSize": 12345,
+    "encrypted": false,
+    "pdfAVersion": "PDF/A-3b",
+    "pdfACompliant": true,
+    "errors": [],
+    "warnings": []
+  }
+  ```
+
+---
+
+#### Test Case 3.2: Non-PDF/A Document
+**Objective:** Verify regular PDFs are detected as non-compliant
+
+**Steps:**
+1. Upload `fake-pdf/one-page.pdf` (regular PDF, NOT PDF/A)
+
+**Expected Result:**
+- **Status Code:** 200 OK
+- **Response:**
+  ```json
+  {
+    "isValid": true,
+    "pdfVersion": "1.4",
+    "pageCount": 1,
+    "fileSize": 7168,
+    "encrypted": false,
+    "pdfAVersion": null,
+    "pdfACompliant": false,
+    "errors": [],
+    "warnings": ["Manual verification recommended: PDF/A compliance requires all fonts to be embedded"]
+  }
+  ```
+
+---
+
+#### Test Case 3.3: Encrypted PDF
+**Objective:** Verify encrypted PDFs are flagged
+
+**Steps:**
+1. Create or obtain a password-protected PDF
+2. Upload via multipart/form-data
+
+**Expected Result:**
+- **Status Code:** 200 OK
+- **Response:**
+  ```json
+  {
+    "isValid": true,
+    "pdfVersion": "1.7",
+    "pageCount": 1,
+    "fileSize": 12345,
+    "encrypted": true,
+    "pdfAVersion": null,
+    "pdfACompliant": false,
+    "errors": ["Encrypted PDFs cannot be PDF/A compliant"],
+    "warnings": []
+  }
+  ```
+
+---
+
+#### Test Case 3.4: Invalid Base64 (PDF/A Endpoint)
+**Objective:** Verify validation works on PDF/A endpoint
+
+**Steps:**
+1. Select **application/json**
+2. Paste:
+   ```json
+   {
+     "base64Pdf": "not-base64!!!"
+   }
+   ```
+
+**Expected Result:**
+- **Status Code:** 400 Bad Request
+- **Error Message:** Contains "Base64"
+
+---
+
+#### Test Case 3.5: Empty Request
+**Objective:** Verify both inputs missing is rejected
+
+**Steps:**
+1. Select **application/json**
+2. Paste:
+   ```json
+   {
+     "pdfBytes": null,
+     "base64Pdf": ""
+   }
+   ```
+
+**Expected Result:**
+- **Status Code:** 400 Bad Request
+- **Error Message:** "Either PdfBytes or Base64Pdf must be provided, but not both"
+
+---
+
+## Feature 2: Swiss QR Code Extraction
+
+### Endpoint: `POST /api/swissqrcode/extract`
+
+#### Test Case 2.1: PDF with Swiss QR Code
+**Objective:** Extract Swiss QR Bill from PDF
+
+**Steps:**
+1. Open Swagger UI → `/api/swissqrcode/extract`
+2. Select **multipart/form-data**
+3. Upload a PDF containing Swiss QR Code on the **last page**
+4. Click "Execute"
+
+**Expected Result (if QR code present):**
+- **Status Code:** 200 OK
+- **Response:** Contains Swiss QR Bill details (IBAN, amount, creditor, debtor, reference)
+
+---
+
+#### Test Case 2.2: PDF without QR Code
+**Objective:** Verify graceful handling when no QR code exists
+
+**Steps:**
+1. Upload `fake-pdf/one-page.pdf` (no QR code)
+
+**Expected Result:**
+- **Status Code:** 404 Not Found
+- **Error Message:** "Swiss QR Code not found in PDF"
+
+---
+
+## Common Error Scenarios
+
+### Test Case E1: Missing File in Multipart Request
+**Steps:**
+1. Any multipart endpoint
+2. Don't select a file, click "Execute"
+
+**Expected Result:**
+- **Status Code:** 400 Bad Request
+
+---
+
+### Test Case E2: Both PdfBytes AND Base64Pdf Provided
+**Steps:**
+1. Attempt to send JSON with both fields populated
+   ```json
+   {
+     "pdfBytes": [1,2,3],
+     "base64Pdf": "dGVzdA=="
+   }
+   ```
+
+**Expected Result:**
+- **Status Code:** 400 Bad Request
+- **Error Message:** "Either PdfBytes or Base64Pdf must be provided, but not both"
+
+---
+
+### Test Case E3: Corrupted PDF File
+**Steps:**
+1. Create a text file with `.pdf` extension containing "FAKE PDF CONTENT"
+2. Upload it
+
+**Expected Result:**
+- **Status Code:** 500 Internal Server Error
+- **Error Message:** Contains "PDF processing error"
+
+---
+
+## Test Coverage Summary
+
+| Feature | Endpoint | Test Cases |
+|---------|----------|------------|
+| Basic PDF Validation | `POST /api/pdf/validation/validate` | 6 |
+| PDF/A Validation | `POST /api/pdf/validation/validate-pdfa` | 5 |
+| Swiss QR Code | `POST /api/swissqrcode/extract` | 2 |
+| Error Handling | All endpoints | 3 |
+| **TOTAL** | | **16 Manual Test Cases** |
+
+---
+
+## Notes
+
+- All endpoints support **BOTH** `multipart/form-data` (file upload) AND `application/json` (Base64)
+- FluentValidation runs before handlers (400 errors indicate validation failures)
+- DevExpress evaluation warnings (DX1000/DX1001) are expected and can be ignored
+- Test PDFs in `fake-pdf/` folder are small samples; use real-world PDFs for comprehensive testing
+
+---
+
+## Quick PowerShell Helpers
+
+**Convert PDF to Base64:**
+```powershell
+$bytes = [System.IO.File]::ReadAllBytes("path\to\file.pdf")
+$base64 = [Convert]::ToBase64String($bytes)
+$base64 | Set-Clipboard  # Copies to clipboard
+```
+
+**Create empty PDF for testing:**
+```powershell
+New-Item -Path "empty.pdf" -ItemType File -Force
+```
+
+**Check if file is valid PDF:**
+```powershell
+$header = Get-Content -Path "file.pdf" -TotalCount 1 -Encoding Byte
+# Should start with: 0x25 0x50 0x44 0x46 (%PDF)
+```

DocumentService.API/appsettings.Development.json

@@ -5,8 +5,8 @@
     }
   },
 
-  "DocumentOperatorSettings": {
-    "TempFolderPath": "C:\\Temp\\DocumentOperator\\Dev",
+  "DocumentServiceSettings": {
+    "TempFolderPath": "C:\\Temp\\DocumentService\\Dev",
     "EnableDetailedLogging": true
   },
 

DocumentService.API/appsettings.json

@@ -0,0 +1,102 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  },
+  "AllowedHosts": "*",
+
+  "Application": {
+    "LogDirectory": "E:\\LogFiles\\Digital Data\\DocumentService.API"
+  },
+
+  "SwaggerSettings": {
+    "EnableInProduction": true,
+    "Title": "DocumentService API",
+    "Version": "v1",
+    "Description": "PDF document processing service using DevExpress"
+  },
+
+  "Serilog": {
+    "MinimumLevel": {
+      "Default": "Information",
+      "Override": {
+        "Microsoft": "Warning",
+        "Microsoft.AspNetCore": "Warning",
+        "System": "Warning"
+      }
+    },
+    "WriteTo": [
+      {
+        "Name": "Console",
+        "Args": {
+          "outputTemplate": "[{Timestamp:HH:mm:ss} {Level:u3}] {Message:lj} {Properties:j}{NewLine}{Exception}"
+        }
+      },
+      {
+        "Name": "File",
+        "Args": {
+          "path": "Logs/log-.txt",
+          "rollingInterval": "Day",
+          "outputTemplate": "{Timestamp:yyyy-MM-dd HH:mm:ss.fff zzz} [{Level:u3}] {Message:lj} {Properties:j}{NewLine}{Exception}"
+        }
+      },
+      {
+        "Name": "SQLite",
+        "Args": {
+          "sqliteDbPath": "E:\\LogFiles\\Digital Data\\DocumentService.API\\logs.db",
+          "tableName": "Logs",
+          "storeTimestampInUtc": true
+        }
+      }
+    ],
+    "Enrich": [ "FromLogContext", "WithMachineName", "WithThreadId" ]
+  },
+
+  "DocumentServiceSettings": {
+    "TempFolderPath": "C:\\Temp\\DocumentService",
+    "TempFileRetentionHours": 24,
+    "MaxPdfSizeMB": 50,
+    "EnableDetailedLogging": true
+  },
+
+  "ZugferdSettings": {
+    "ZugferdFileNames": [
+      "factur-x.xml",
+      "zugferd-invoice.xml",
+      "ZUGFeRD-invoice.xml",
+      "xrechnung.xml",
+      "XRechnung.xml"
+    ],
+    "ZugferdFileNamePatterns": [
+      "factur",
+      "zugferd",
+      "xrechnung",
+      "peppol"
+    ]
+  },
+
+  "RedisSettings": {
+    "ConnectionString": "localhost:6379",
+    "InstanceName": "DocumentService:",
+    "CacheExpirationMinutes": 60
+  },
+
+  "ApiKeySettings": {
+    "EnableValidation": true,
+    "Keys": {
+      "customer-a-key-12345": {
+        "TenantId": "customer-a",
+        "TenantName": "Customer A GmbH",
+        "IsActive": true
+      },
+      "customer-b-key-67890": {
+        "TenantId": "customer-b",
+        "TenantName": "Customer B AG",
+        "IsActive": true
+      }
+    }
+  },
+  "LuckyPennySoftLicenseKey": "eyJhbGciOiJSUzI1NiIsImtpZCI6Ikx1Y2t5UGVubnlTb2Z0d2FyZUxpY2Vuc2VLZXkvYmJiMTNhY2I1OTkwNGQ4OWI0Y2IxYzg1ZjA4OGNjZjkiLCJ0eXAiOiJKV1QifQ.eyJpc3MiOiJodHRwczovL2x1Y2t5cGVubnlzb2Z0d2FyZS5jb20iLCJhdWQiOiJMdWNreVBlbm55U29mdHdhcmUiLCJleHAiOiIxODE2MTI4MDAwIiwiaWF0IjoiMTc4NDYyNDU1NyIsImFjY291bnRfaWQiOiIwMTk4M2M1OWU0YjM3MjhlYmZkMzEwM2MyYTQ4NmU4NSIsImN1c3RvbWVyX2lkIjoiMDE5ODNjNTllNGIzNzI4ZWJmZDMxMDNjMmE0ODZlODUiLCJzdWJfaWQiOiItIiwiZWRpdGlvbiI6IjAiLCJ0eXBlIjoiMiJ9.IUUO926m9crYGYxMjjKD_n9BnUm-EDyjFIn0YmMUCo7C-QTwvB8WhXP8veTSFsBq-leIIDJ4jyl7Pgc_7ciwg1XhUSIs4mkQroEUaSFCGOxw7Pi41WM8MK5YFSaqLTYYXec9zxgiJbGzABbh3CHTSup3okGnVm_CMoPEs91l2c0A6N1JyZy74urd_tF0KGVKf0MOvzdlQIWLQ8o73S4pTv2N-F6UlzI0fdMtTHMLNNQyr0NdWdnuBk_jMBXO-gy5RE_oCRfMTTYRX2n3XLK6pTfXE0Ct338o9F5sH8Ph2lTXSu56cpdsfZOQZGqCH0LoFp1Dd7RJgIgNmBiTGfvDnA"
+}

DocumentService.Application/AddAnnotation/AddAnnotationCommand.cs

@@ -0,0 +1,78 @@
+using DocumentService.Application.Common.Interfaces;
+using DocumentService.Domain.Models.ValueObjects;
+using FluentValidation;
+using MediatR;
+
+namespace DocumentService.Application.AddAnnotation;
+
+/// <summary>
+/// Command to add an annotation to a PDF document.
+/// </summary>
+public record AddAnnotationCommand : IRequest<byte[]>
+{
+    public required Stream PdfStream { get; init; }
+    public required AnnotationType AnnotationType { get; init; }
+    public required int PageNumber { get; init; }
+    public required (double X1, double Y1, double X2, double Y2) Rectangle { get; init; }
+    public string? Content { get; init; }
+    public string? Author { get; init; }
+    public string? Color { get; init; }
+    public TextMarkupStyle? TextMarkupStyle { get; init; }
+    public AnnotationOrigin Origin { get; init; } = AnnotationOrigin.BottomLeft;
+}
+
+/// <summary>
+/// Handler for AddAnnotationCommand.
+/// </summary>
+public class AddAnnotationHandler(IPdfProcessor pdfProcessor) : IRequestHandler<AddAnnotationCommand, byte[]>
+{
+    public async Task<byte[]> Handle(AddAnnotationCommand request, CancellationToken cancellationToken)
+    {
+        return await pdfProcessor.AddAnnotationAsync(
+            request.PdfStream,
+            request.AnnotationType,
+            request.PageNumber,
+            request.Rectangle,
+            request.Content,
+            request.Author,
+            request.Color,
+            request.TextMarkupStyle,
+            request.Origin);
+    }
+}
+
+/// <summary>
+/// Validator for AddAnnotationCommand.
+/// </summary>
+public class AddAnnotationValidator : AbstractValidator<AddAnnotationCommand>
+{
+    public AddAnnotationValidator()
+    {
+        RuleFor(x => x.PdfStream)
+            .NotNull()
+            .WithMessage("PDF stream is required");
+
+        RuleFor(x => x.PageNumber)
+            .GreaterThan(0)
+            .WithMessage("Page number must be greater than 0");
+
+        RuleFor(x => x.Content)
+            .NotEmpty()
+            .When(x => x.AnnotationType == AnnotationType.FreeText || x.AnnotationType == AnnotationType.StickyNote)
+            .WithMessage("Content is required for FreeText and StickyNote annotations");
+
+        RuleFor(x => x.TextMarkupStyle)
+            .NotNull()
+            .When(x => x.AnnotationType == AnnotationType.TextMarkup)
+            .WithMessage("TextMarkupStyle is required for TextMarkup annotations");
+
+        RuleFor(x => x.Color)
+            .Matches("^[0-9A-Fa-f]{6}$")
+            .When(x => !string.IsNullOrWhiteSpace(x.Color))
+            .WithMessage("Color must be a 6-digit hex value (e.g., 'FF0000' for red)");
+
+        RuleFor(x => x.Rectangle)
+            .Must(r => r.X2 > r.X1 && r.Y2 > r.Y1)
+            .WithMessage("Rectangle coordinates must define a valid area (X2 > X1 and Y2 > Y1)");
+    }
+}

DocumentService.Application/AddAttachments/AddAttachmentsCommand.cs

@@ -0,0 +1,90 @@
+using DocumentService.Application.Common.Interfaces;
+using FluentValidation;
+using MediatR;
+
+namespace DocumentService.Application.AddAttachments;
+
+/// <summary>
+/// Command to add one or more attachments to a PDF document (supports PDF/A-3)
+/// </summary>
+public record AddAttachmentsCommand : IRequest<byte[]>
+{
+    /// <summary>
+    /// PDF document stream. Must be positioned at the beginning (Position = 0).
+    /// </summary>
+    public required Stream PdfStream { get; init; }
+
+    /// <summary>
+    /// List of attachments to embed (filename, content, optional MIME type)
+    /// </summary>
+    public required IReadOnlyList<AttachmentFile> Attachments { get; init; }
+}
+
+/// <summary>
+/// Represents a file to be attached to a PDF
+/// </summary>
+public record AttachmentFile
+{
+    /// <summary>
+    /// File name (e.g., "invoice.xml", "document.pdf")
+    /// </summary>
+    public required string FileName { get; init; }
+
+    /// <summary>
+    /// File content as byte array
+    /// </summary>
+    public required byte[] Content { get; init; }
+
+    /// <summary>
+    /// MIME type (optional, e.g., "application/xml", "application/pdf")
+    /// If not provided, will be inferred from file extension
+    /// </summary>
+    public string? MimeType { get; init; }
+}
+
+/// <summary>
+/// Handler for AddAttachmentsCommand
+/// </summary>
+public class AddAttachmentsCommandHandler(IPdfProcessor pdfProcessor) 
+    : IRequestHandler<AddAttachmentsCommand, byte[]>
+{
+    public async Task<byte[]> Handle(AddAttachmentsCommand request, CancellationToken cancellationToken)
+    {
+        // Convert to tuple list for IPdfProcessor
+        var attachmentTuples = request.Attachments
+            .Select(a => (a.FileName, a.Content, a.MimeType))
+            .ToList();
+
+        return await pdfProcessor.AddAttachmentsAsync(request.PdfStream, attachmentTuples);
+    }
+}
+
+/// <summary>
+/// Validator for AddAttachmentsCommand
+/// </summary>
+public class AddAttachmentsCommandValidator : AbstractValidator<AddAttachmentsCommand>
+{
+    public AddAttachmentsCommandValidator()
+    {
+        RuleFor(x => x.PdfStream)
+            .NotNull()
+            .WithMessage("PDF stream is required");
+
+        RuleFor(x => x.Attachments)
+            .NotNull()
+            .NotEmpty()
+            .WithMessage("At least one attachment is required");
+
+        RuleForEach(x => x.Attachments).ChildRules(attachment =>
+        {
+            attachment.RuleFor(a => a.FileName)
+                .NotEmpty()
+                .WithMessage("Attachment file name is required");
+
+            attachment.RuleFor(a => a.Content)
+                .NotNull()
+                .NotEmpty()
+                .WithMessage("Attachment content is required");
+        });
+    }
+}

DocumentService.Application/AddStamp/AddStampCommand.cs

@@ -0,0 +1,125 @@
+using FluentValidation;
+using MediatR;
+
+namespace DocumentService.Application.AddStamp;
+
+/// <summary>
+/// Command to add a stamp (text, image, or predefined) to PDF pages.
+/// Combines Command, Handler, and Validator in a single file (Vertical Slice pattern).
+/// </summary>
+public record AddStampCommand : IRequest<byte[]>
+{
+    public required Stream PdfStream { get; init; }
+    public required Domain.Models.ValueObjects.StampType StampType { get; init; }
+    public int[]? PageNumbers { get; init; } // null = all pages
+    public required (double X, double Y) Position { get; init; }
+    public (double Width, double Height)? Size { get; init; }
+    public Domain.Models.ValueObjects.AnnotationOrigin Origin { get; init; } = Domain.Models.ValueObjects.AnnotationOrigin.BottomLeft;
+    public string? Text { get; init; }
+    public string? FontName { get; init; }
+    public double? FontSize { get; init; }
+    public string? Color { get; init; }
+    public double? Opacity { get; init; }
+    public double? Rotation { get; init; }
+    public Domain.Models.ValueObjects.StampPlacement Placement { get; init; } = Domain.Models.ValueObjects.StampPlacement.Foreground;
+    public byte[]? ImageBytes { get; init; }
+    public Domain.Models.ValueObjects.PredefinedStampType? PredefinedType { get; init; }
+}
+
+/// <summary>
+/// Handler for AddStampCommand.
+/// </summary>
+public class AddStampHandler(Common.Interfaces.IPdfProcessor pdfProcessor) : IRequestHandler<AddStampCommand, byte[]>
+{
+    public async Task<byte[]> Handle(AddStampCommand command, CancellationToken cancellationToken)
+    {
+        return await pdfProcessor.AddStampAsync(
+            command.PdfStream,
+            command.StampType,
+            command.PageNumbers,
+            command.Position,
+            command.Size,
+            command.Origin,
+            command.Text,
+            command.FontName,
+            command.FontSize,
+            command.Color,
+            command.Opacity,
+            command.Rotation,
+            command.Placement,
+            command.ImageBytes,
+            command.PredefinedType
+        );
+    }
+}
+
+/// <summary>
+/// Validator for AddStampCommand.
+/// </summary>
+public class AddStampValidator : AbstractValidator<AddStampCommand>
+{
+    public AddStampValidator()
+    {
+        RuleFor(x => x.PdfStream)
+            .NotNull().WithMessage("PDF stream is required");
+
+        RuleFor(x => x.Position.X)
+            .GreaterThanOrEqualTo(0).WithMessage("Position X must be >= 0");
+
+        RuleFor(x => x.Position.Y)
+            .GreaterThanOrEqualTo(0).WithMessage("Position Y must be >= 0");
+
+        // Text stamp validation
+        When(x => x.StampType == Domain.Models.ValueObjects.StampType.Text, () =>
+        {
+            RuleFor(x => x.Text)
+                .NotEmpty().WithMessage("Text is required for Text stamp type");
+        });
+
+        // Image stamp validation
+        When(x => x.StampType == Domain.Models.ValueObjects.StampType.Image, () =>
+        {
+            RuleFor(x => x.ImageBytes)
+                .NotNull().WithMessage("Image bytes are required for Image stamp type")
+                .Must(bytes => bytes != null && bytes.Length > 0).WithMessage("Image bytes cannot be empty");
+        });
+
+        // Predefined stamp validation
+        When(x => x.StampType == Domain.Models.ValueObjects.StampType.Predefined, () =>
+        {
+            RuleFor(x => x.PredefinedType)
+                .NotNull().WithMessage("Predefined type is required for Predefined stamp type");
+        });
+
+        // Optional parameter validations
+        When(x => x.Opacity.HasValue, () =>
+        {
+            RuleFor(x => x.Opacity!.Value)
+                .InclusiveBetween(0.0, 1.0).WithMessage("Opacity must be between 0.0 and 1.0");
+        });
+
+        When(x => x.Rotation.HasValue, () =>
+        {
+            RuleFor(x => x.Rotation!.Value)
+                .InclusiveBetween(0.0, 360.0).WithMessage("Rotation must be between 0 and 360 degrees");
+        });
+
+        When(x => x.FontSize.HasValue, () =>
+        {
+            RuleFor(x => x.FontSize!.Value)
+                .GreaterThan(0).WithMessage("Font size must be positive");
+        });
+
+        When(x => !string.IsNullOrWhiteSpace(x.Color), () =>
+        {
+            RuleFor(x => x.Color!)
+                .Matches(@"^[0-9A-Fa-f]{6}$").WithMessage("Color must be 6-digit hex (e.g., 'FF0000')");
+        });
+
+        When(x => x.PageNumbers != null, () =>
+        {
+            RuleFor(x => x.PageNumbers!)
+                .Must(pages => pages.All(p => p > 0)).WithMessage("All page numbers must be >= 1");
+        });
+    }
+}

DocumentService.Application/CheckPdfAttachments/Queries/CheckPdfAttachmentsQuery.cs

@@ -0,0 +1,37 @@
+using AutoMapper;
+using DocumentService.Application.Common.DTOs;
+using DocumentService.Application.Common.Interfaces;
+using MediatR;
+
+namespace DocumentService.Application.CheckPdfAttachments.Queries;
+
+/// <summary>
+/// Query for checking PDF attachments (Stream-based)
+/// </summary>
+public record CheckPdfAttachmentsQuery : IRequest<AttachmentCheckResult>
+{
+    /// <summary>
+    /// PDF as stream (caller is responsible for disposal)
+    /// </summary>
+    public required Stream PdfStream { get; init; }
+}
+
+/// <summary>
+/// Handler for CheckPdfAttachmentsQuery
+/// Orchestrates PDF attachment checking using IPdfProcessor and AutoMapper
+/// </summary>
+public class CheckPdfAttachmentsQueryHandler(IPdfProcessor PdfProcessor, IMapper Mapper)
+    : IRequestHandler<CheckPdfAttachmentsQuery, AttachmentCheckResult>
+{
+    /// <summary>
+    /// Checks PDF attachments and returns detailed metadata
+    /// </summary>
+    public async Task<AttachmentCheckResult> Handle(CheckPdfAttachmentsQuery request, CancellationToken cancellationToken)
+    {
+        // Call DevExpress service directly with stream (exceptions propagate naturally)
+        var attachmentInfo = await PdfProcessor.CheckAttachmentsAsync(request.PdfStream);
+
+        // Map DTO to response DTO using AutoMapper
+        return Mapper.Map<AttachmentCheckResult>(attachmentInfo);
+    }
+}

DocumentService.Application/CheckPdfAttachments/Queries/CheckPdfAttachmentsQueryValidator.cs

@@ -0,0 +1,18 @@
+using FluentValidation;
+
+namespace DocumentService.Application.CheckPdfAttachments.Queries;
+
+/// <summary>
+/// Validator for CheckPdfAttachmentsQuery
+/// Ensures PdfStream is not null
+/// </summary>
+public class CheckPdfAttachmentsQueryValidator : AbstractValidator<CheckPdfAttachmentsQuery>
+{
+    public CheckPdfAttachmentsQueryValidator()
+    {
+        // Rule: PdfStream must be provided and non-empty
+        RuleFor(x => x.PdfStream)
+            .NotNull()
+            .WithMessage("PdfStream is required");
+    }
+}

DocumentService.Application/Common/Behaviors/LoggingBehavior.cs

@@ -0,0 +1,56 @@
+using MediatR;
+using Microsoft.Extensions.Logging;
+using System.Diagnostics;
+
+namespace DocumentService.Application.Common.Behaviors;
+
+/// <summary>
+/// MediatR Pipeline Behavior that logs requests and tracks performance
+/// Executes AFTER ValidationBehavior, BEFORE Handler
+/// </summary>
+public class LoggingBehavior<TRequest, TResponse>(ILogger<LoggingBehavior<TRequest, TResponse>> Logger) : IPipelineBehavior<TRequest, TResponse>
+    where TRequest : IRequest<TResponse>
+{
+    public async Task<TResponse> Handle(
+        TRequest request,
+        RequestHandlerDelegate<TResponse> next,
+        CancellationToken cancellationToken)
+    {
+        var requestName = typeof(TRequest).Name;
+
+        // Performance Tracking
+        var stopwatch = Stopwatch.StartNew();
+
+        try
+        {
+            // Handler ausführen
+            var response = await next(cancellationToken);
+
+            stopwatch.Stop();
+
+            // Request Success
+            Logger.LogInformation(
+                "Handled {RequestName} in {ElapsedMs}ms",
+                requestName,
+                stopwatch.ElapsedMilliseconds
+            );
+
+            return response;
+        }
+        catch (Exception ex)
+        {
+            stopwatch.Stop();
+
+            // Request Failed
+            Logger.LogError(
+                ex,
+                "Error handling {RequestName} after {ElapsedMs}ms: {ErrorMessage}",
+                requestName,
+                stopwatch.ElapsedMilliseconds,
+                ex.Message
+            );
+
+            throw; // Exception weiterwerfen (wird von Exception Middleware gefangen)
+        }
+    }
+}

DocumentService.Application/Common/Behaviors/ValidationBehavior.cs

@@ -0,0 +1,54 @@
+using FluentValidation;
+using MediatR;
+
+namespace DocumentService.Application.Common.Behaviors;
+
+/// <summary>
+/// MediatR Pipeline Behavior that validates requests using FluentValidation
+/// Executes BEFORE the Handler
+/// </summary>
+public class ValidationBehavior<TRequest, TResponse> : IPipelineBehavior<TRequest, TResponse>
+    where TRequest : IRequest<TResponse>
+{
+    private readonly IEnumerable<IValidator<TRequest>> _validators;
+
+    public ValidationBehavior(IEnumerable<IValidator<TRequest>> validators)
+    {
+        _validators = validators;
+    }
+
+    public async Task<TResponse> Handle(
+        TRequest request,
+        RequestHandlerDelegate<TResponse> next,
+        CancellationToken cancellationToken)
+    {
+        // Wenn keine Validators registriert sind, direkt weiter zum Handler
+        if (!_validators.Any())
+        {
+            return await next();
+        }
+
+        // Validation Context erstellen
+        var context = new ValidationContext<TRequest>(request);
+
+        // Alle Validators parallel ausführen
+        var validationResults = await Task.WhenAll(
+            _validators.Select(v => v.ValidateAsync(context, cancellationToken))
+        );
+
+        // Fehler sammeln
+        var failures = validationResults
+            .Where(r => !r.IsValid)
+            .SelectMany(r => r.Errors)
+            .ToList();
+
+        // Bei Fehlern: ValidationException werfen (wird von Exception Middleware gefangen)
+        if (failures.Any())
+        {
+            throw new ValidationException(failures);
+        }
+
+        // Validation erfolgreich ? weiter zum Handler
+        return await next();
+    }
+}

DocumentService.Application/Common/Configuration/ZugferdSettings.cs

@@ -0,0 +1,29 @@
+namespace DocumentService.Application.Common.Configuration;
+
+/// <summary>
+/// Configuration settings for ZUGFeRD/Factur-X/XRechnung detection
+/// </summary>
+public class ZugferdSettings
+{
+    /// <summary>
+    /// Exact ZUGFeRD/Factur-X/XRechnung file names to check (case-insensitive)
+    /// </summary>
+    public List<string> ZugferdFileNames { get; set; } = new()
+    {
+        "factur-x.xml",
+        "zugferd-invoice.xml",
+        "ZUGFeRD-invoice.xml",
+        "xrechnung.xml"
+    };
+    
+    /// <summary>
+    /// Partial filename patterns for ZUGFeRD detection (case-insensitive)
+    /// </summary>
+    public List<string> ZugferdFileNamePatterns { get; set; } = new()
+    {
+        "factur",
+        "zugferd",
+        "xrechnung",
+        "peppol"
+    };
+}

DocumentService.Application/Common/DTOs/AttachmentCheckResult.cs

@@ -0,0 +1,43 @@
+namespace DocumentService.Application.Common.DTOs;
+
+/// <summary>
+/// DTO for attachment check result returned to API layer
+/// </summary>
+public record AttachmentCheckResult
+{
+    /// <summary>
+    /// Indicates whether the PDF contains any attachments
+    /// </summary>
+    public bool HasAttachments { get; init; }
+
+    /// <summary>
+    /// Total number of attachments in the PDF
+    /// </summary>
+    public int AttachmentCount { get; init; }
+
+    /// <summary>
+    /// List of attachment metadata (file details)
+    /// </summary>
+    public List<AttachmentDto> Attachments { get; init; } = new();
+}
+
+/// <summary>
+/// DTO for individual attachment metadata
+/// </summary>
+public record AttachmentDto
+{
+    /// <summary>
+    /// Attachment file name (e.g., "invoice.xml", "document.pdf")
+    /// </summary>
+    public string FileName { get; init; } = string.Empty;
+
+    /// <summary>
+    /// MIME type of the attachment (e.g., "text/xml", "application/pdf")
+    /// </summary>
+    public string MimeType { get; init; } = string.Empty;
+
+    /// <summary>
+    /// Attachment file size in bytes
+    /// </summary>
+    public long Size { get; init; }
+}

DocumentService.Application/Common/DTOs/AttachmentInfo.cs

@@ -0,0 +1,60 @@
+namespace DocumentService.Application.Common.DTOs;
+
+/// <summary>
+/// Represents complete attachment information for a PDF document.
+/// Immutable value object containing attachment presence flag, count, and detailed metadata.
+/// </summary>
+public sealed class AttachmentInfo
+{
+    /// <summary>
+    /// Gets a value indicating whether the PDF contains any attachments
+    /// </summary>
+    public bool HasAttachments { get; }
+
+    /// <summary>
+    /// Gets the total number of attachments in the PDF
+    /// </summary>
+    public int AttachmentCount { get; }
+
+    /// <summary>
+    /// Gets the collection of attachment metadata (file details)
+    /// </summary>
+    public IReadOnlyList<AttachmentMetadata> Attachments { get; }
+
+    /// <summary>
+    /// Initializes a new instance of the AttachmentInfo class.
+    /// </summary>
+    /// <param name="hasAttachments">Whether PDF has attachments</param>
+    /// <param name="attachmentCount">Total number of attachments</param>
+    /// <param name="attachments">List of attachment metadata (can be empty)</param>
+    public AttachmentInfo(bool hasAttachments, int attachmentCount, IReadOnlyList<AttachmentMetadata> attachments)
+    {
+        HasAttachments = hasAttachments;
+        AttachmentCount = attachmentCount;
+        Attachments = attachments ?? [];
+
+        // Defensive Programming: Ensure count matches list length
+        if (Attachments.Count != attachmentCount)
+        {
+            throw new ArgumentException(
+                $"Attachment count mismatch: expected {attachmentCount}, got {Attachments.Count}",
+                nameof(attachments));
+        }
+    }
+
+    /// <summary>
+    /// Creates an AttachmentInfo instance for a PDF with no attachments.
+    /// </summary>
+    public static AttachmentInfo Empty =>
+        new(
+            hasAttachments: false,
+            attachmentCount: 0,
+            attachments: []);
+
+    public override string ToString()
+    {
+        return HasAttachments
+            ? $"PDF has {AttachmentCount} attachment(s): {string.Join(", ", Attachments.Select(a => a.FileName))}"
+            : "PDF has no attachments";
+    }
+}

DocumentService.Application/Common/DTOs/AttachmentMetadata.cs

@@ -0,0 +1,44 @@
+namespace DocumentService.Application.Common.DTOs;
+
+/// <summary>
+/// Represents metadata of a single PDF attachment (embedded file).
+/// Immutable value object containing file information without the actual binary data.
+/// </summary>
+/// <remarks>
+/// Initializes a new instance of the AttachmentMetadata class.
+/// </remarks>
+/// <param name="fileName">Attachment file name</param>
+/// <param name="mimeType">MIME type (e.g., "text/xml")</param>
+/// <param name="sizeBytes">File size in bytes</param>
+public sealed class AttachmentMetadata(string fileName, string mimeType, long sizeBytes)
+{
+    /// <summary>
+    /// Gets the attachment file name (e.g., "invoice.xml", "document.pdf")
+    /// </summary>
+    public string FileName { get; } = fileName ?? string.Empty;
+
+    /// <summary>
+    /// Gets the MIME type of the attachment (e.g., "text/xml", "application/pdf")
+    /// </summary>
+    public string MimeType { get; } = mimeType ?? "application/octet-stream"; // Default MIME type if unknown
+
+    /// <summary>
+    /// Gets the attachment file size in bytes
+    /// </summary>
+    public long SizeBytes { get; } = sizeBytes;
+
+    /// <summary>
+    /// Gets the attachment file size in kilobytes (computed property)
+    /// </summary>
+    public double SizeKB => SizeBytes / 1024.0;
+
+    /// <summary>
+    /// Gets the attachment file size in megabytes (computed property)
+    /// </summary>
+    public double SizeMB => SizeBytes / 1024.0 / 1024.0;
+
+    public override string ToString()
+    {
+        return $"{FileName} ({MimeType}, {SizeKB:F2} KB)";
+    }
+}

DocumentService.Application/Common/DTOs/PdfAValidationResult.cs

@@ -0,0 +1,52 @@
+namespace DocumentService.Application.Common.DTOs;
+
+/// <summary>
+/// PDF/A validation result including conformance level and validation errors/warnings
+/// </summary>
+public record PdfAValidationResult
+{
+    /// <summary>
+    /// Whether the PDF is valid (no errors)
+    /// </summary>
+    public bool IsValid { get; init; }
+
+    /// <summary>
+    /// PDF version (e.g., "1.4", "1.7")
+    /// </summary>
+    public string PdfVersion { get; init; } = string.Empty;
+
+    /// <summary>
+    /// Number of pages in the PDF
+    /// </summary>
+    public int PageCount { get; init; }
+
+    /// <summary>
+    /// File size in bytes
+    /// </summary>
+    public long FileSize { get; init; }
+
+    /// <summary>
+    /// Whether the PDF is encrypted
+    /// </summary>
+    public bool Encrypted { get; init; }
+
+    /// <summary>
+    /// PDF/A version (e.g., "PDF/A-1b", "PDF/A-2a", "PDF/A-3u") or null if not PDF/A compliant
+    /// </summary>
+    public string? PdfAVersion { get; init; }
+
+    /// <summary>
+    /// Whether the PDF conforms to PDF/A standard
+    /// </summary>
+    public bool PdfACompliant { get; init; }
+
+    /// <summary>
+    /// Validation errors (e.g., "PDF/A documents cannot be encrypted")
+    /// </summary>
+    public IReadOnlyList<string> Errors { get; init; } = [];
+
+    /// <summary>
+    /// Validation warnings (e.g., "Manual verification recommended: All fonts must be embedded")
+    /// </summary>
+    public IReadOnlyList<string> Warnings { get; init; } = [];
+}

DocumentService.Application/Common/DTOs/PdfValidationResult.cs

@@ -0,0 +1,23 @@
+namespace DocumentService.Application.Common.DTOs;
+
+/// <summary>
+/// Response mit PDF-Metadaten
+/// </summary>
+/// <param name="PageCount">Anzahl der Seiten</param>
+/// <param name="FileSizeBytes">Dateigröße in Bytes</param>
+/// <param name="FileSizeMB">Dateigröße in MB (gerundet auf 2 Dezimalstellen)</param>
+/// <param name="PdfVersion">PDF-Version (z.B. "1.4")</param>
+/// <param name="HasAttachments">Hat das PDF Anhänge?</param>
+/// <param name="AttachmentCount">Anzahl der Anhänge</param>
+/// <param name="IsEncrypted">Ist das PDF passwortgeschützt/verschlüsselt?</param>
+public record PdfValidationResult(
+    int PageCount,
+    long FileSizeBytes,
+    double FileSizeMB,
+    string PdfVersion,
+    bool HasAttachments,
+    int AttachmentCount,
+    bool IsEncrypted)
+{
+    public bool IsValid => !IsEncrypted && PageCount > 0 && FileSizeBytes > 0;
+}

DocumentService.Application/Common/DTOs/Requests/PdfAttachmentRequests.cs

@@ -0,0 +1,46 @@
+namespace DocumentService.Application.Common.DTOs.Requests;
+
+/// <summary>
+/// Request DTO for Base64-encoded PDF attachment check
+/// </summary>
+public record CheckPdfAttachmentsRequest : PdfBase64RequestBase;
+
+/// <summary>
+/// Request DTO for Base64-encoded PDF attachment extraction
+/// </summary>
+public record ExtractPdfAttachmentsRequest : PdfBase64RequestBase;
+
+/// <summary>
+/// Request DTO for Base64-encoded PDF with attachments to add
+/// </summary>
+public record AddAttachmentsRequest : PdfBase64RequestBase
+{
+    /// <summary>
+    /// List of attachments to embed
+    /// </summary>
+    public required List<AttachmentRequestDto> Attachments { get; init; }
+}
+
+/// <summary>
+/// DTO for a single attachment file in a request
+/// </summary>
+public record AttachmentRequestDto
+{
+    /// <summary>
+    /// File name (e.g., "invoice.xml", "document.pdf")
+    /// </summary>
+    /// <example>factur-x.xml</example>
+    public required string FileName { get; init; }
+
+    /// <summary>
+    /// File content encoded as Base64 string
+    /// </summary>
+    /// <example>PD94bWwgdmVyc2lvbj0iMS4wIj8+...</example>
+    public required string Base64Content { get; init; }
+
+    /// <summary>
+    /// MIME type (optional, e.g., "application/xml")
+    /// </summary>
+    /// <example>application/xml</example>
+    public string? MimeType { get; init; }
+}

DocumentService.Application/Common/DTOs/Requests/PdfBase64RequestBase.cs

@@ -0,0 +1,14 @@
+namespace DocumentService.Application.Common.DTOs.Requests;
+
+/// <summary>
+/// Base record for all single-PDF Base64 request types.
+/// Provides the common <see cref="Base64Pdf"/> property shared across endpoints.
+/// </summary>
+public abstract record PdfBase64RequestBase
+{
+    /// <summary>
+    /// PDF document encoded as Base64 string
+    /// </summary>
+    /// <example>JVBERi0xLjQKJeLjz9MKMSAwIG9iago8PC9UeXBlL0NhdGFsb2c...</example>
+    public required string Base64Pdf { get; init; }
+}

DocumentService.Application/Common/DTOs/Requests/PdfConversionRequests.cs

@@ -0,0 +1,18 @@
+namespace DocumentService.Application.Common.DTOs.Requests;
+
+/// <summary>
+/// Request DTO for converting a standard PDF to PDF/A format (Base64 JSON)
+/// </summary>
+public record ConvertToPdfARequest : PdfBase64RequestBase
+{
+    /// <summary>
+    /// Target PDF/A conformance level. Defaults to "PDF/A-3b".
+    /// </summary>
+    /// <example>PDF/A-3b</example>
+    public string? PdfALevel { get; init; }
+}
+
+/// <summary>
+/// Request DTO for converting a PDF/A document back to standard PDF (Base64 JSON)
+/// </summary>
+public record ConvertFromPdfARequest : PdfBase64RequestBase;

DocumentService.Application/Common/DTOs/Requests/PdfOperationRequests.cs

@@ -0,0 +1,209 @@
+using DocumentService.Domain.Models.ValueObjects;
+
+namespace DocumentService.Application.Common.DTOs.Requests;
+
+/// <summary>
+/// Request DTO for Base64-encoded PDF merge operation
+/// </summary>
+public record MergePdfsBase64Request
+{
+    /// <summary>
+    /// Array of Base64-encoded PDF files (minimum 2 required)
+    /// </summary>
+    /// <example>["JVBERi0xLjQK...", "JVBERi0xLjQK..."]</example>
+    public required List<string> Base64Pdfs { get; init; }
+
+    /// <summary>
+    /// Optional page ranges per PDF (null = all pages). 
+    /// Format: "1-3,5" means pages 1, 2, 3, and 5.
+    /// If provided, array length must match Base64Pdfs length.
+    /// </summary>
+    /// <example>["1-2", "1,3,5", null]</example>
+    public List<string?>? PageRanges { get; init; }
+}
+
+/// <summary>
+/// Request DTO for Base64-encoded PDF annotation
+/// </summary>
+public record AddAnnotationBase64Request : PdfBase64RequestBase
+{
+    /// <summary>
+    /// Type of annotation to add
+    /// </summary>
+    /// <example>TextMarkup</example>
+    public required AnnotationType AnnotationType { get; init; }
+
+    /// <summary>
+    /// Target page number (1-indexed)
+    /// </summary>
+    /// <example>1</example>
+    public required int PageNumber { get; init; }
+
+    /// <summary>
+    /// Rectangle X1 coordinate (left)
+    /// </summary>
+    /// <example>100.0</example>
+    public required double X1 { get; init; }
+
+    /// <summary>
+    /// Rectangle Y1 coordinate (top or bottom depending on Origin)
+    /// </summary>
+    /// <example>100.0</example>
+    public required double Y1 { get; init; }
+
+    /// <summary>
+    /// Rectangle X2 coordinate (right). Optional if Width is provided.
+    /// </summary>
+    /// <example>200.0</example>
+    public double? X2 { get; init; }
+
+    /// <summary>
+    /// Rectangle Y2 coordinate (bottom or top depending on Origin). Optional if Height is provided.
+    /// </summary>
+    /// <example>120.0</example>
+    public double? Y2 { get; init; }
+
+    /// <summary>
+    /// Rectangle width. Alternative to X2 (X2 = X1 + Width). Optional if X2 is provided.
+    /// </summary>
+    /// <example>100.0</example>
+    public double? Width { get; init; }
+
+    /// <summary>
+    /// Rectangle height. Alternative to Y2 (Y2 = Y1 + Height). Optional if Y2 is provided.
+    /// </summary>
+    /// <example>20.0</example>
+    public double? Height { get; init; }
+
+    /// <summary>
+    /// Annotation content (required for FreeText and StickyNote)
+    /// </summary>
+    /// <example>"Important text to highlight"</example>
+    public string? Content { get; init; }
+
+    /// <summary>
+    /// Author name (optional)
+    /// </summary>
+    /// <example>"John Doe"</example>
+    public string? Author { get; init; }
+
+    /// <summary>
+    /// Hex color (6 digits, e.g., "FF0000" for red). Optional - defaults vary by annotation type.
+    /// </summary>
+    /// <example>"FFFF00"</example>
+    public string? Color { get; init; }
+
+    /// <summary>
+    /// Text markup style (Highlight, Underline, or Strikeout). Required for TextMarkup annotations.
+    /// </summary>
+    /// <example>Highlight</example>
+    public TextMarkupStyle? TextMarkupStyle { get; init; }
+
+    /// <summary>
+    /// Coordinate origin (BottomLeft = PDF native, TopLeft = UI-friendly). Default: BottomLeft
+    /// </summary>
+    /// <example>BottomLeft</example>
+    public AnnotationOrigin Origin { get; init; } = AnnotationOrigin.BottomLeft;
+}
+
+/// <summary>
+/// Request DTO for Base64-encoded PDF stamp operation
+/// </summary>
+public record AddStampBase64Request : PdfBase64RequestBase
+{
+    /// <summary>
+    /// Type of stamp (Text, Image, or Predefined)
+    /// </summary>
+    /// <example>Text</example>
+    public required StampType StampType { get; init; }
+
+    /// <summary>
+    /// Target page numbers (1-indexed). Null or empty = all pages.
+    /// </summary>
+    /// <example>[1, 3, 5]</example>
+    public int[]? PageNumbers { get; init; }
+
+    /// <summary>
+    /// Stamp position X coordinate
+    /// </summary>
+    /// <example>100.0</example>
+    public required double X { get; init; }
+
+    /// <summary>
+    /// Stamp position Y coordinate
+    /// </summary>
+    /// <example>100.0</example>
+    public required double Y { get; init; }
+
+    /// <summary>
+    /// Stamp width (optional, auto-size for images if not specified)
+    /// </summary>
+    /// <example>200.0</example>
+    public double? Width { get; init; }
+
+    /// <summary>
+    /// Stamp height (optional, auto-size for images if not specified)
+    /// </summary>
+    /// <example>50.0</example>
+    public double? Height { get; init; }
+
+    /// <summary>
+    /// Coordinate origin (BottomLeft = PDF native, TopLeft = UI-friendly). Default: BottomLeft
+    /// </summary>
+    /// <example>BottomLeft</example>
+    public AnnotationOrigin Origin { get; init; } = AnnotationOrigin.BottomLeft;
+
+    /// <summary>
+    /// Text content (required for Text stamps)
+    /// </summary>
+    /// <example>"CONFIDENTIAL"</example>
+    public string? Text { get; init; }
+
+    /// <summary>
+    /// Font name (default: Arial)
+    /// </summary>
+    /// <example>"Arial"</example>
+    public string? FontName { get; init; }
+
+    /// <summary>
+    /// Font size in points (default: 12)
+    /// </summary>
+    /// <example>24.0</example>
+    public double? FontSize { get; init; }
+
+    /// <summary>
+    /// Hex color (6 digits, e.g., "FF0000" for red, default: "000000")
+    /// </summary>
+    /// <example>"FF0000"</example>
+    public string? Color { get; init; }
+
+    /// <summary>
+    /// Opacity (0.0 = transparent, 1.0 = opaque, default: 0.5)
+    /// </summary>
+    /// <example>0.5</example>
+    public double? Opacity { get; init; }
+
+    /// <summary>
+    /// Rotation angle in degrees (0-360, default: 0)
+    /// </summary>
+    /// <example>45.0</example>
+    public double? Rotation { get; init; }
+
+    /// <summary>
+    /// Stamp placement (Foreground = on top, Background = watermark effect, default: Foreground)
+    /// </summary>
+    /// <example>Foreground</example>
+    public StampPlacement Placement { get; init; } = StampPlacement.Foreground;
+
+    /// <summary>
+    /// Base64-encoded image (required for Image stamps, PNG/JPEG)
+    /// </summary>
+    /// <example>"iVBORw0KGgoAAAANSUhEUgAA..."</example>
+    public string? Base64Image { get; init; }
+
+    /// <summary>
+    /// Predefined stamp type (required for Predefined stamps)
+    /// </summary>
+    /// <example>Confidential</example>
+    public PredefinedStampType? PredefinedType { get; init; }
+}

DocumentService.Application/Common/DTOs/Requests/PdfValidationRequests.cs

@@ -0,0 +1,11 @@
+namespace DocumentService.Application.Common.DTOs.Requests;
+
+/// <summary>
+/// Request DTO for Base64-encoded PDF validation
+/// </summary>
+public record ValidatePdfBase64Request : PdfBase64RequestBase;
+
+/// <summary>
+/// Request DTO for Base64-encoded PDF/A validation
+/// </summary>
+public record ValidatePdfABase64Request : PdfBase64RequestBase;

DocumentService.Application/Common/DTOs/Requests/SwissQrCodeRequests.cs

@@ -0,0 +1,6 @@
+namespace DocumentService.Application.Common.DTOs.Requests;
+
+/// <summary>
+/// Request DTO for Base64-encoded Swiss QR Code extraction
+/// </summary>
+public record ExtractSwissQrCodeBase64Request : PdfBase64RequestBase;

DocumentService.Application/Common/DTOs/Requests/ZugferdRequests.cs

@@ -0,0 +1,11 @@
+namespace DocumentService.Application.Common.DTOs.Requests;
+
+/// <summary>
+/// Request DTO for Base64-encoded PDF ZUGFeRD check
+/// </summary>
+public record HasZugferdRequest : PdfBase64RequestBase;
+
+/// <summary>
+/// Request DTO for Base64-encoded PDF ZUGFeRD extraction
+/// </summary>
+public record ExtractZugferdRequest : PdfBase64RequestBase;

DocumentService.Application/Common/DTOs/SwissQrBillDto.cs

@@ -0,0 +1,93 @@
+namespace DocumentService.Application.Common.DTOs;
+
+/// <summary>
+/// Swiss QR Bill data transfer object (mapped from Codecrete Bill)
+/// </summary>
+public record SwissQrBillDto
+{
+    /// <summary>QR Bill standard version (e.g., "V2_0")</summary>
+    public required string Version { get; init; }
+
+    /// <summary>Payment amount (null if not specified)</summary>
+    public decimal? Amount { get; init; }
+
+    /// <summary>Payment currency (CHF or EUR)</summary>
+    public required string Currency { get; init; }
+
+    /// <summary>Creditor's IBAN account number</summary>
+    public required string Account { get; init; }
+
+    /// <summary>Creditor address</summary>
+    public required AddressDto Creditor { get; init; }
+
+    /// <summary>Payment reference type: "QRR", "SCOR", or "NON"</summary>
+    public required string ReferenceType { get; init; }
+
+    /// <summary>Payment reference (format depends on ReferenceType)</summary>
+    public string? Reference { get; init; }
+
+    /// <summary>Debtor address (optional)</summary>
+    public AddressDto? Debtor { get; init; }
+
+    /// <summary>Additional unstructured message (max 140 chars)</summary>
+    public string? UnstructuredMessage { get; init; }
+
+    /// <summary>Additional structured bill information</summary>
+    public string? BillInformation { get; init; }
+
+    /// <summary>Alternative payment schemes (max 2)</summary>
+    public IReadOnlyList<AlternativeSchemeDto>? AlternativeSchemes { get; init; }
+}
+
+/// <summary>
+/// Address data transfer object (mapped from Codecrete Address)
+/// </summary>
+public record AddressDto
+{
+    /// <summary>Address type: "Structured" or "CombinedElements"</summary>
+    public required string Type { get; init; }
+
+    /// <summary>Name of person or company</summary>
+    public required string Name { get; init; }
+
+    /// <summary>Street name (structured address only)</summary>
+    public string? Street { get; init; }
+
+    /// <summary>House number (structured address only)</summary>
+    public string? HouseNo { get; init; }
+
+    /// <summary>
+    /// Address line 1 (combined address only).
+    /// OBSOLETE: Use structured address instead. Will be removed when Codecrete v4 is adopted.
+    /// </summary>
+    [Obsolete("Use structured address (Street + HouseNo) instead. This field will be removed when upgrading to Codecrete.SwissQRBill.Generator v4.x")]
+    public string? AddressLine1 { get; init; }
+
+    /// <summary>
+    /// Address line 2 (combined address only).
+    /// OBSOLETE: Use structured address instead. Will be removed when Codecrete v4 is adopted.
+    /// </summary>
+    [Obsolete("Use structured address (Street + HouseNo) instead. This field will be removed when upgrading to Codecrete.SwissQRBill.Generator v4.x")]
+    public string? AddressLine2 { get; init; }
+
+    /// <summary>Postal code</summary>
+    public required string PostalCode { get; init; }
+
+    /// <summary>Town/city name</summary>
+    public required string Town { get; init; }
+
+    /// <summary>Two-letter country code (ISO 3166-1 alpha-2)</summary>
+    public required string CountryCode { get; init; }
+}
+
+/// <summary>
+/// Alternative payment scheme (mapped from Codecrete AlternativeScheme)
+/// </summary>
+public record AlternativeSchemeDto
+{
+    /// <summary>Scheme name (e.g., "AV1", "AV2")</summary>
+    public required string Name { get; init; }
+
+    /// <summary>Scheme instruction/parameter</summary>
+    public required string Instruction { get; init; }
+}

DocumentService.Application/Common/DTOs/SwissQrCodeExtractionResult.cs

@@ -0,0 +1,41 @@
+namespace DocumentService.Application.Common.DTOs;
+
+/// <summary>
+/// Response containing extracted Swiss QR Code in dual format.
+/// </summary>
+/// <param name="Bill">Parsed Swiss QR Bill (structured format)</param>
+/// <param name="RawLines">Raw Swiss QR Code lines (original newline-separated format)</param>
+/// <example>
+/// {
+///   "bill": {
+///     "version": "V2_0",
+///     "amount": 630.20,
+///     "currency": "CHF",
+///     "account": "CH953000520280564701R",
+///     "creditor": {
+///       "type": "Structured",
+///       "name": "ALMAT AG",
+///       "town": "Tagelswangen"
+///     },
+///     "referenceType": "QRR",
+///     "reference": "000000000000000000252080824"
+///   },
+///   "rawLines": [
+///     "SPC",
+///     "0200",
+///     "1",
+///     "CH953000520280564701R",
+///     "S",
+///     "ALMAT AG",
+///     "..."
+///   ]
+/// }
+/// </example>
+public record SwissQrCodeExtractionResult(
+#if NET
+    SwissQrBillDto Bill,
+#else
+    object? Bill,
+#endif
+    IEnumerable<string> RawLines
+);

DocumentService.Application/Common/DTOs/ZugferdCheckResult.cs

@@ -0,0 +1,27 @@
+namespace DocumentService.Application.Common.DTOs;
+
+/// <summary>
+/// DTO for ZUGFeRD check result
+/// </summary>
+public record ZugferdCheckResult
+{
+    /// <summary>
+    /// Indicates whether the PDF contains ZUGFeRD XML attachment
+    /// </summary>
+    public bool HasZugferd { get; init; }
+
+    /// <summary>
+    /// ZUGFeRD XML file name (e.g., "factur-x.xml")
+    /// </summary>
+    public string? ZugferdFileName { get; init; }
+
+    /// <summary>
+    /// ZUGFeRD XML file size in bytes
+    /// </summary>
+    public long? ZugferdFileSize { get; init; }
+
+    /// <summary>
+    /// MIME type of the ZUGFeRD XML file
+    /// </summary>
+    public string? ZugferdMimeType { get; init; }
+}

DocumentService.Application/Common/Interfaces/IPdfProcessor.cs

@@ -0,0 +1,191 @@
+using DocumentService.Application.Common.DTOs;
+
+namespace DocumentService.Application.Common.Interfaces;
+
+public interface IPdfProcessor
+{
+    /// <summary>
+    /// Validates a PDF and extracts metadata.
+    /// </summary>
+    /// <param name="pdfStream">
+    /// PDF document stream. Must be readable and positioned at the beginning (Position = 0).
+    /// Non-seekable streams are supported. Caller is responsible for disposal.
+    /// </param>
+    /// <returns>PDF metadata (page count, size, version, attachments)</returns>
+    /// <exception cref="Domain.Common.Exceptions.BadRequestException">
+    /// Thrown when stream is empty, invalid, or not positioned at the beginning
+    /// </exception>
+    Task<PdfValidationResult> ValidateAsync(Stream pdfStream);
+
+    /// <summary>
+    /// Validates a PDF/A document and checks conformance level.
+    /// </summary>
+    /// <param name="pdfStream">
+    /// PDF document stream. Must be readable and positioned at the beginning (Position = 0).
+    /// Non-seekable streams are supported. Caller is responsible for disposal.
+    /// </param>
+    /// <returns>PDF/A metadata including conformance level and validation errors/warnings</returns>
+    /// <exception cref="Domain.Common.Exceptions.BadRequestException">
+    /// Thrown when stream is empty, invalid, or not positioned at the beginning
+    /// </exception>
+    Task<PdfAValidationResult> ValidatePdfAAsync(Stream pdfStream);
+
+    /// <summary>
+    /// Checks for embedded files (attachments) in a PDF document and returns detailed metadata.
+    /// </summary>
+    /// <param name="pdfStream">
+    /// PDF document stream. Must be readable and positioned at the beginning (Position = 0).
+    /// Non-seekable streams are supported. Caller is responsible for disposal.
+    /// </param>
+    /// <returns>Attachment information (count, file names, MIME types, sizes)</returns>
+    /// <exception cref="Domain.Common.Exceptions.BadRequestException">
+    /// Thrown when stream is empty, invalid, or not positioned at the beginning
+    /// </exception>
+    Task<AttachmentInfo> CheckAttachmentsAsync(Stream pdfStream);
+
+    /// <summary>
+    /// Extracts all embedded files from a PDF document and returns them as a ZIP archive.
+    /// </summary>
+    /// <param name="pdfStream">
+    /// PDF document stream. Must be readable and positioned at the beginning (Position = 0).
+    /// Non-seekable streams are supported. Caller is responsible for disposal.
+    /// </param>
+    /// <returns>ZIP archive containing all extracted attachments as byte array</returns>
+    /// <exception cref="Domain.Common.Exceptions.BadRequestException">
+    /// Thrown when stream is empty, invalid, or not positioned at the beginning
+    /// </exception>
+    /// <exception cref="Domain.Common.Exceptions.NotFoundException">
+    /// Thrown when PDF contains no attachments
+    /// </exception>
+    Task<byte[]> ExtractAttachmentsAsync(Stream pdfStream);
+
+    /// <summary>
+    /// Merges multiple PDF documents into a single PDF.
+    /// </summary>
+    /// <param name="pdfStreams">
+    /// PDF streams to merge (minimum 2 required). Each stream must be readable and positioned 
+    /// at the beginning (Position = 0). Caller is responsible for disposal.
+    /// </param>
+    /// <param name="pageRanges">
+    /// Optional page ranges per PDF (null = all pages). Format: "1-3,5" means pages 1, 2, 3, and 5.
+    /// If null or empty for a PDF, all pages are included. Array length must match pdfStreams length if provided.
+    /// </param>
+    /// <returns>Merged PDF as byte array</returns>
+    /// <exception cref="Domain.Common.Exceptions.BadRequestException">
+    /// Thrown when fewer than 2 PDFs provided, any stream is empty/invalid/not at Position=0, 
+    /// or page range format is invalid
+    /// </exception>
+    Task<byte[]> MergePdfsAsync(IReadOnlyList<Stream> pdfStreams, IReadOnlyList<string?>? pageRanges = null);
+
+    /// <summary>
+    /// Adds an annotation to a PDF document at the specified page and rectangle.
+    /// </summary>
+    /// <param name="pdfStream">
+    /// PDF document stream. Must be readable and positioned at the beginning (Position = 0).
+    /// Non-seekable streams are supported. Caller is responsible for disposal.
+    /// </param>
+    /// <param name="annotationType">Type of annotation to add (TextMarkup, FreeText, StickyNote, Circle, Square)</param>
+    /// <param name="pageNumber">Page number (1-based) where annotation should be added</param>
+    /// <param name="rectangle">Annotation bounding rectangle (X1, Y1, X2, Y2)</param>
+    /// <param name="content">Annotation content/comment text (required for FreeText and StickyNote)</param>
+    /// <param name="author">Optional author name</param>
+    /// <param name="color">Optional annotation color in RGB format (hex string like "FF0000" for red)</param>
+    /// <param name="textMarkupStyle">Text markup style (Highlight, Underline, Strikeout) - only for TextMarkup type</param>
+    /// <param name="origin">Coordinate origin (BottomLeft = PDF native, TopLeft = UI-friendly). Default: BottomLeft</param>
+    /// <returns>Annotated PDF as byte array</returns>
+    /// <exception cref="Domain.Common.Exceptions.BadRequestException">
+    /// Thrown when stream is empty/invalid/not at Position=0, page number out of range, 
+    /// rectangle invalid, or content missing for types that require it
+    /// </exception>
+    Task<byte[]> AddAnnotationAsync(
+        Stream pdfStream,
+        Domain.Models.ValueObjects.AnnotationType annotationType,
+        int pageNumber,
+        (double X1, double Y1, double X2, double Y2) rectangle,
+        string? content = null,
+        string? author = null,
+        string? color = null,
+        Domain.Models.ValueObjects.TextMarkupStyle? textMarkupStyle = null,
+        Domain.Models.ValueObjects.AnnotationOrigin origin = Domain.Models.ValueObjects.AnnotationOrigin.BottomLeft);
+
+    /// <summary>
+    /// Adds a stamp (text, image, or predefined) to specified pages of a PDF document.
+    /// </summary>
+    /// <param name="pdfStream">Input PDF stream (must support reading and seeking)</param>
+    /// <param name="stampType">Type of stamp (Text, Image, or Predefined)</param>
+    /// <param name="pageNumbers">Target page numbers (1-based). Null = all pages.</param>
+    /// <param name="position">Stamp position (X, Y coordinates)</param>
+    /// <param name="size">Stamp size (Width, Height). Null = auto-size for images.</param>
+    /// <param name="origin">Coordinate origin (BottomLeft or TopLeft)</param>
+    /// <param name="text">Text content (required for Text stamps)</param>
+    /// <param name="fontName">Font name (default: Arial)</param>
+    /// <param name="fontSize">Font size in points (default: 12)</param>
+    /// <param name="color">Hex color without # (e.g., "FF0000" for red, default: "000000")</param>
+    /// <param name="opacity">Opacity 0.0 (transparent) to 1.0 (opaque, default: 0.5)</param>
+    /// <param name="rotation">Rotation angle in degrees 0-360 (default: 0)</param>
+    /// <param name="placement">Foreground (on top) or Background (behind content)</param>
+    /// <param name="imageBytes">Image data (required for Image stamps, PNG/JPEG)</param>
+    /// <param name="predefinedType">Predefined stamp type (required for Predefined stamps)</param>
+    /// <returns>Stamped PDF as byte array</returns>
+    /// <exception cref="BadRequestException">Invalid parameters (missing text/image, invalid page numbers, invalid opacity/rotation)</exception>
+    /// <exception cref="PdfProcessingException">DevExpress processing error</exception>
+    Task<byte[]> AddStampAsync(
+        Stream pdfStream,
+        Domain.Models.ValueObjects.StampType stampType,
+        int[]? pageNumbers,
+        (double X, double Y) position,
+        (double Width, double Height)? size = null,
+        Domain.Models.ValueObjects.AnnotationOrigin origin = Domain.Models.ValueObjects.AnnotationOrigin.BottomLeft,
+        string? text = null,
+        string? fontName = null,
+        double? fontSize = null,
+        string? color = null,
+        double? opacity = null,
+        double? rotation = null,
+        Domain.Models.ValueObjects.StampPlacement placement = Domain.Models.ValueObjects.StampPlacement.Foreground,
+        byte[]? imageBytes = null,
+        Domain.Models.ValueObjects.PredefinedStampType? predefinedType = null);
+
+    /// <summary>
+    /// Embeds one or more files as attachments in a PDF document (supports PDF/A-3).
+    /// </summary>
+    /// <param name="pdfStream">
+    /// PDF document stream. Must be readable and positioned at the beginning (Position = 0).
+    /// Non-seekable streams are supported. Caller is responsible for disposal.
+    /// </param>
+    /// <param name="attachments">List of files to embed (filename, content, optional MIME type)</param>
+    /// <returns>PDF with embedded attachments as byte array</returns>
+    /// <exception cref="Domain.Common.Exceptions.BadRequestException">
+    /// Thrown when stream is empty/invalid, or attachments list is empty
+    /// </exception>
+    Task<byte[]> AddAttachmentsAsync(
+        Stream pdfStream, 
+        IReadOnlyList<(string FileName, byte[] Content, string? MimeType)> attachments);
+
+    /// <summary>
+    /// Converts a standard PDF to PDF/A format.
+    /// </summary>
+    /// <param name="pdfStream">
+    /// PDF document stream. Must be readable and positioned at the beginning (Position = 0).
+    /// Non-seekable streams are supported. Caller is responsible for disposal.
+    /// </param>
+    /// <param name="pdfALevel">Target PDF/A level (e.g., "PDF/A-1b", "PDF/A-2b", "PDF/A-3b")</param>
+    /// <returns>PDF/A compliant document as byte array</returns>
+    /// <exception cref="Domain.Common.Exceptions.BadRequestException">
+    /// Thrown when stream is empty/invalid or PDF/A level is unsupported
+    /// </exception>
+    Task<byte[]> ConvertToPdfAAsync(Stream pdfStream, string pdfALevel);
+
+    /// <summary>
+    /// Converts a PDF/A document to a standard PDF (removes PDF/A restrictions).
+    /// </summary>
+    /// <param name="pdfStream">
+    /// PDF/A document stream. Must be readable and positioned at the beginning (Position = 0).
+    /// Non-seekable streams are supported. Caller is responsible for disposal.
+    /// </param>
+    /// <returns>Standard PDF document as byte array</returns>
+    /// <exception cref="Domain.Common.Exceptions.BadRequestException">
+    /// Thrown when stream is empty/invalid
+    /// </exception>
+    Task<byte[]> ConvertFromPdfAAsync(Stream pdfStream);
+}

DocumentService.Application/Common/Interfaces/ISwissQrCodeProcessor.cs

@@ -0,0 +1,32 @@
+using Codecrete.SwissQRBill.Generator;
+
+namespace DocumentService.Application.Common.Interfaces;
+
+/// <summary>
+/// Interface for Swiss QR Code processing operations.
+/// Extracts and parses Swiss QR Codes from PDF documents.
+/// </summary>
+public interface ISwissQrCodeProcessor
+{
+    /// <summary>
+    /// Extracts and parses Swiss QR Code from a PDF document.
+    /// Returns both parsed Bill object and raw QR text lines.
+    /// </summary>
+    /// <param name="pdfStream">
+    /// PDF document stream. Must be readable and positioned at the beginning (Position = 0).
+    /// Non-seekable streams are supported. Caller is responsible for disposal.
+    /// </param>
+    /// <param name="pageNumbers">Optional: Specific page numbers to scan (1-indexed). If null, scans all pages starting with last page.</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>Tuple: (Parsed Codecrete Bill, Raw QR lines as string array)</returns>
+    /// <exception cref="Domain.Common.Exceptions.NotFoundException">
+    /// Thrown when no Swiss QR Code is found in the specified pages
+    /// </exception>
+    /// <exception cref="ArgumentException">
+    /// Thrown when stream is empty or (for seekable streams) not positioned at the beginning
+    /// </exception>
+    Task<(Bill Bill, string[] RawLines)> ExtractSwissQrCodeAsync(
+        Stream pdfStream, 
+        int[]? pageNumbers = null, 
+        CancellationToken cancellationToken = default);
+}

DocumentService.Application/Common/Mapping/MappingProfile.cs

@@ -0,0 +1,48 @@
+using AutoMapper;
+using Codecrete.SwissQRBill.Generator;
+using DocumentService.Application.Common.DTOs;
+using DocumentService.Domain.Models.ValueObjects;
+
+namespace DocumentService.Application.Common.Mapping;
+
+/// <summary>
+/// AutoMapper profile for mapping domain entities and external models to DTOs.
+/// NOTE: Always use AutoMapper for all mappings in this project.
+/// </summary>
+public class MappingProfile : Profile
+{
+    public MappingProfile()
+    {
+
+        // Codecrete Bill -> SwissQrBillDto
+        CreateMap<Bill, SwissQrBillDto>()
+            .ForMember(dest => dest.Version, opt => opt.MapFrom(src => src.Version.ToString()))
+            .ForMember(dest => dest.Currency, opt => opt.MapFrom(src => src.Currency ?? "CHF"))
+            .ForMember(dest => dest.Account, opt => opt.MapFrom(src => src.Account ?? string.Empty))
+            .ForMember(dest => dest.ReferenceType, opt => opt.MapFrom(src => src.ReferenceType ?? Bill.ReferenceTypeNoRef));
+
+        // Codecrete Address -> AddressDto
+        CreateMap<Address, AddressDto>()
+            .ForMember(dest => dest.Type, opt => opt.MapFrom(src => src.Type.ToString()))
+            .ForMember(dest => dest.Name, opt => opt.MapFrom(src => src.Name ?? string.Empty))
+            .ForMember(dest => dest.PostalCode, opt => opt.MapFrom(src => src.PostalCode ?? string.Empty))
+            .ForMember(dest => dest.Town, opt => opt.MapFrom(src => src.Town ?? string.Empty))
+            .ForMember(dest => dest.CountryCode, opt => opt.MapFrom(src => src.CountryCode ?? string.Empty))
+#pragma warning disable CS0618 // Suppress obsolete warning for AddressLine1/2 mapping
+            .ForMember(dest => dest.AddressLine1, opt => opt.MapFrom(src => src.AddressLine1))
+            .ForMember(dest => dest.AddressLine2, opt => opt.MapFrom(src => src.AddressLine2));
+#pragma warning restore CS0618
+
+        // Codecrete AlternativeScheme -> AlternativeSchemeDto
+        CreateMap<AlternativeScheme, AlternativeSchemeDto>()
+            .ForMember(dest => dest.Name, opt => opt.MapFrom(src => src.Name ?? string.Empty))
+            .ForMember(dest => dest.Instruction, opt => opt.MapFrom(src => src.Instruction ?? string.Empty));
+
+        // AttachmentInfo -> AttachmentCheckResult
+        CreateMap<AttachmentInfo, AttachmentCheckResult>();
+
+        // AttachmentMetadata -> AttachmentDto
+        CreateMap<AttachmentMetadata, AttachmentDto>()
+            .ForMember(dest => dest.Size, opt => opt.MapFrom(src => src.SizeBytes));
+    }
+}

DocumentService.Application/ConvertFromPdfA/ConvertFromPdfACommand.cs

@@ -0,0 +1,41 @@
+using DocumentService.Application.Common.Interfaces;
+using FluentValidation;
+using MediatR;
+
+namespace DocumentService.Application.ConvertFromPdfA;
+
+/// <summary>
+/// Command to convert a PDF/A document to a standard PDF (removes PDF/A restrictions)
+/// </summary>
+public record ConvertFromPdfACommand : IRequest<byte[]>
+{
+    /// <summary>
+    /// PDF/A document stream. Must be positioned at the beginning (Position = 0).
+    /// </summary>
+    public required Stream PdfStream { get; init; }
+}
+
+/// <summary>
+/// Handler for ConvertFromPdfACommand
+/// </summary>
+public class ConvertFromPdfACommandHandler(IPdfProcessor pdfProcessor) 
+    : IRequestHandler<ConvertFromPdfACommand, byte[]>
+{
+    public async Task<byte[]> Handle(ConvertFromPdfACommand request, CancellationToken cancellationToken)
+    {
+        return await pdfProcessor.ConvertFromPdfAAsync(request.PdfStream);
+    }
+}
+
+/// <summary>
+/// Validator for ConvertFromPdfACommand
+/// </summary>
+public class ConvertFromPdfACommandValidator : AbstractValidator<ConvertFromPdfACommand>
+{
+    public ConvertFromPdfACommandValidator()
+    {
+        RuleFor(x => x.PdfStream)
+            .NotNull()
+            .WithMessage("PDF stream is required");
+    }
+}

DocumentService.Application/ConvertToPdfA/ConvertToPdfACommand.cs

@@ -0,0 +1,59 @@
+using DocumentService.Application.Common.Interfaces;
+using FluentValidation;
+using MediatR;
+
+namespace DocumentService.Application.ConvertToPdfA;
+
+/// <summary>
+/// Command to convert a standard PDF to PDF/A format
+/// </summary>
+public record ConvertToPdfACommand : IRequest<byte[]>
+{
+    /// <summary>
+    /// PDF document stream. Must be positioned at the beginning (Position = 0).
+    /// </summary>
+    public required Stream PdfStream { get; init; }
+
+    /// <summary>
+    /// Target PDF/A level (e.g., "PDF/A-1b", "PDF/A-2b", "PDF/A-3b")
+    /// </summary>
+    public required string PdfALevel { get; init; }
+}
+
+/// <summary>
+/// Handler for ConvertToPdfACommand
+/// </summary>
+public class ConvertToPdfACommandHandler(IPdfProcessor pdfProcessor) 
+    : IRequestHandler<ConvertToPdfACommand, byte[]>
+{
+    public async Task<byte[]> Handle(ConvertToPdfACommand request, CancellationToken cancellationToken)
+    {
+        return await pdfProcessor.ConvertToPdfAAsync(request.PdfStream, request.PdfALevel);
+    }
+}
+
+/// <summary>
+/// Validator for ConvertToPdfACommand
+/// </summary>
+public class ConvertToPdfACommandValidator : AbstractValidator<ConvertToPdfACommand>
+{
+    private static readonly string[] ValidPdfALevels = 
+    {
+        "PDF/A-1b", "PDF/A-1a",
+        "PDF/A-2b", "PDF/A-2u", "PDF/A-2a",
+        "PDF/A-3b", "PDF/A-3u", "PDF/A-3a"
+    };
+
+    public ConvertToPdfACommandValidator()
+    {
+        RuleFor(x => x.PdfStream)
+            .NotNull()
+            .WithMessage("PDF stream is required");
+
+        RuleFor(x => x.PdfALevel)
+            .NotEmpty()
+            .WithMessage("PDF/A level is required")
+            .Must(level => ValidPdfALevels.Contains(level, StringComparer.OrdinalIgnoreCase))
+            .WithMessage($"Invalid PDF/A level. Valid values: {string.Join(", ", ValidPdfALevels)}");
+    }
+}

DocumentService.Application/DependencyInjection.cs

@@ -0,0 +1,44 @@
+using FluentValidation;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace DocumentService.Application;
+
+/// <summary>
+/// Dependency Injection configuration for Application Layer
+/// </summary>
+public static class DependencyInjection
+{
+    /// <summary>
+    /// Registers Application Layer services (MediatR, FluentValidation, AutoMapper, Behaviors)
+    /// </summary>
+    public static IServiceCollection AddApplication(this IServiceCollection services, IConfiguration configuration)
+    {
+        var assembly = typeof(DependencyInjection).Assembly;
+
+        // Read LuckyPennySoft license key from appsettings.json
+        var licenseKey = configuration.GetValue<string>("LuckyPennySoftLicenseKey")
+            ?? throw new InvalidOperationException("LuckyPennySoftLicenseKey not found in configuration");
+
+        // Register MediatR (scannt Assembly nach Handlers)
+        services.AddMediatR(config =>
+        {
+            config.LicenseKey = licenseKey;
+            config.RegisterServicesFromAssembly(assembly);
+
+            // Pipeline Behaviors (Reihenfolge wichtig!)
+            config.AddOpenBehavior(typeof(Common.Behaviors.ValidationBehavior<,>));
+            config.AddOpenBehavior(typeof(Common.Behaviors.LoggingBehavior<,>));
+        });
+
+        // Register FluentValidation (scannt Assembly nach Validators)
+        services.AddValidatorsFromAssembly(assembly);
+
+        // Register AutoMapper (scannt Assembly nach Profiles)
+        services.AddAutoMapper(cfg => {
+            cfg.LicenseKey = licenseKey;
+        }, typeof(Common.Mapping.MappingProfile));
+
+        return services;
+    }
+}

DocumentService.Application/DocumentService.Application.csproj

@@ -0,0 +1,65 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFrameworks>net462;net480;net8.0</TargetFrameworks>
+    <ImplicitUsings>enable</ImplicitUsings>
+	<Nullable>enable</Nullable>
+	<LangVersion>latest</LangVersion>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Remove="DependencyInjection\**" />
+    <Compile Remove="Features\**" />
+    <EmbeddedResource Remove="DependencyInjection\**" />
+    <EmbeddedResource Remove="Features\**" />
+    <None Remove="DependencyInjection\**" />
+    <None Remove="Features\**" />
+  </ItemGroup>
+
+  <ItemGroup Condition="'$(TargetFramework)' == 'net8.0'">
+    <PackageReference Include="AutoMapper" Version="16.2.0" />
+    <PackageReference Include="Codecrete.SwissQRBill.Generator" Version="3.4.0" />
+    <PackageReference Include="FluentValidation" Version="12.1.1" />
+    <PackageReference Include="FluentValidation.DependencyInjectionExtensions" Version="12.1.1" />
+    <PackageReference Include="MediatR" Version="14.1.0" />
+    <PackageReference Include="Microsoft.Extensions.Configuration.Abstractions" Version="10.0.10" />
+    <PackageReference Include="Microsoft.Extensions.Configuration.Binder" Version="10.0.10" />
+  </ItemGroup>
+
+  <ItemGroup Condition="'$(TargetFramework)' == 'net462'">
+    <PackageReference Include="AutoMapper" Version="16.2.0" />
+    <PackageReference Include="FluentValidation" Version="11.11.0" />
+    <PackageReference Include="MediatR" Version="14.1.0" />
+    <PackageReference Include="Microsoft.Extensions.Configuration.Abstractions" Version="8.0.0" />
+    <PackageReference Include="Microsoft.Extensions.Configuration.Binder" Version="8.0.2" />
+  </ItemGroup>
+
+  <ItemGroup Condition="'$(TargetFramework)' == 'net480'">
+    <PackageReference Include="AutoMapper" Version="16.2.0" />
+    <PackageReference Include="FluentValidation" Version="11.11.0" />
+    <PackageReference Include="MediatR" Version="14.1.0" />
+    <PackageReference Include="Microsoft.Extensions.Configuration.Abstractions" Version="8.0.0" />
+    <PackageReference Include="Microsoft.Extensions.Configuration.Binder" Version="8.0.2" />
+  </ItemGroup>
+
+  <ItemGroup Condition="'$(TargetFramework)' != 'net8.0'">
+    <PackageReference Include="PolySharp" Version="1.14.1">
+      <PrivateAssets>all</PrivateAssets>
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+    </PackageReference>
+  </ItemGroup>
+
+  <ItemGroup Condition="'$(TargetFramework)' != 'net8.0'">
+    <Compile Remove="Common\Interfaces\ISwissQrCodeProcessor.cs" />
+    <Compile Remove="Common\DTOs\SwissQrBillDto.cs" />
+    <Compile Remove="Common\Mapping\MappingProfile.cs" />
+    <Compile Remove="SwissQrCode\**" />
+    <Compile Remove="HasZugferd\**" />
+    <Compile Remove="DependencyInjection.cs" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\DocumentService.Domain\DocumentService.Domain.csproj" />
+  </ItemGroup>
+
+</Project>

DocumentService.Application/ExtractPdfAttachments/ExtractPdfAttachmentsCommand.cs

@@ -0,0 +1,43 @@
+using DocumentService.Application.Common.Interfaces;
+using FluentValidation;
+using MediatR;
+
+namespace DocumentService.Application.ExtractPdfAttachments;
+
+/// <summary>
+/// Command to extract all embedded files from a PDF document and return as ZIP archive.
+/// </summary>
+public record ExtractPdfAttachmentsCommand : IRequest<byte[]>
+{
+    /// <summary>
+    /// PDF document stream. Must be positioned at the beginning (Position = 0).
+    /// </summary>
+    public required Stream PdfStream { get; init; }
+}
+
+/// <summary>
+/// Handler for ExtractPdfAttachmentsCommand.
+/// Extracts all embedded files from PDF and returns as ZIP archive.
+/// </summary>
+public class ExtractPdfAttachmentsCommandHandler(IPdfProcessor pdfProcessor) 
+    : IRequestHandler<ExtractPdfAttachmentsCommand, byte[]>
+{
+    public async Task<byte[]> Handle(ExtractPdfAttachmentsCommand request, CancellationToken cancellationToken)
+    {
+        // Delegate to infrastructure layer
+        return await pdfProcessor.ExtractAttachmentsAsync(request.PdfStream);
+    }
+}
+
+/// <summary>
+/// Validator for ExtractPdfAttachmentsCommand.
+/// </summary>
+public class ExtractPdfAttachmentsCommandValidator : AbstractValidator<ExtractPdfAttachmentsCommand>
+{
+    public ExtractPdfAttachmentsCommandValidator()
+    {
+        RuleFor(x => x.PdfStream)
+            .NotNull()
+            .WithMessage("PDF stream is required");
+    }
+}

DocumentService.Application/ExtractZugferd/ExtractZugferdCommand.cs

@@ -0,0 +1,115 @@
+using DocumentService.Application.Common.Configuration;
+using DocumentService.Application.Common.Interfaces;
+using DocumentService.Domain.Common.Exceptions;
+using FluentValidation;
+using MediatR;
+using Microsoft.Extensions.Options;
+
+namespace DocumentService.Application.ExtractZugferd;
+
+/// <summary>
+/// Command to extract ZUGFeRD XML from a PDF document
+/// </summary>
+public record ExtractZugferdCommand : IRequest<ZugferdExtractionResult>
+{
+    /// <summary>
+    /// PDF document stream. Must be positioned at the beginning (Position = 0).
+    /// </summary>
+    public required Stream PdfStream { get; init; }
+}
+
+#if NET
+/// <summary>
+/// Handler for ExtractZugferdCommand.
+/// Extracts ZUGFeRD XML from PDF and returns XML content
+/// </summary>
+public class ExtractZugferdCommandHandler(
+    IPdfProcessor pdfProcessor,
+    IOptions<ZugferdSettings> settings) 
+    : IRequestHandler<ExtractZugferdCommand, ZugferdExtractionResult>
+{
+    private readonly ZugferdSettings _settings = settings.Value;
+
+    public async Task<ZugferdExtractionResult> Handle(ExtractZugferdCommand request, CancellationToken cancellationToken)
+    {
+        // Get all attachments
+        var attachmentInfo = await pdfProcessor.CheckAttachmentsAsync(request.PdfStream);
+
+        // Find ZUGFeRD XML file using configured names and patterns
+        var zugferdAttachment = attachmentInfo.Attachments.FirstOrDefault(a =>
+            _settings.ZugferdFileNames.Any(name => 
+                a.FileName.Equals(name, StringComparison.OrdinalIgnoreCase)) ||
+            _settings.ZugferdFileNamePatterns.Any(pattern => 
+                a.FileName.Contains(pattern, StringComparison.OrdinalIgnoreCase)));
+
+        if (zugferdAttachment == null)
+        {
+            throw new NotFoundException("ZUGFeRD XML not found in PDF attachments");
+        }
+
+        // Reset stream position for extraction
+        request.PdfStream.Position = 0;
+
+        // Extract all attachments as ZIP
+        byte[] zipBytes = await pdfProcessor.ExtractAttachmentsAsync(request.PdfStream);
+
+        // Find ZUGFeRD XML in ZIP
+        using var zipStream = new MemoryStream(zipBytes);
+        using var zipArchive = new System.IO.Compression.ZipArchive(zipStream, System.IO.Compression.ZipArchiveMode.Read);
+
+        var zugferdEntry = zipArchive.Entries.FirstOrDefault(e =>
+            e.Name.Equals(zugferdAttachment.FileName, StringComparison.OrdinalIgnoreCase));
+
+        if (zugferdEntry == null)
+        {
+            throw new NotFoundException($"ZUGFeRD XML '{zugferdAttachment.FileName}' not found in extracted attachments");
+        }
+
+        // Read XML content
+        using var entryStream = zugferdEntry.Open();
+        using var reader = new StreamReader(entryStream);
+        string xmlContent = await reader.ReadToEndAsync(cancellationToken);
+
+        return new ZugferdExtractionResult
+        {
+            FileName = zugferdAttachment.FileName,
+            XmlContent = xmlContent,
+            FileSize = zugferdAttachment.SizeBytes
+        };
+    }
+}
+#endif
+
+/// <summary>
+/// Validator for ExtractZugferdCommand.
+/// </summary>
+public class ExtractZugferdCommandValidator : AbstractValidator<ExtractZugferdCommand>
+{
+    public ExtractZugferdCommandValidator()
+    {
+        RuleFor(x => x.PdfStream)
+            .NotNull()
+            .WithMessage("PDF stream is required");
+    }
+}
+
+/// <summary>
+/// Result DTO for ZUGFeRD extraction
+/// </summary>
+public record ZugferdExtractionResult
+{
+    /// <summary>
+    /// ZUGFeRD XML file name
+    /// </summary>
+    public required string FileName { get; init; }
+
+    /// <summary>
+    /// ZUGFeRD XML content as string
+    /// </summary>
+    public required string XmlContent { get; init; }
+
+    /// <summary>
+    /// File size in bytes
+    /// </summary>
+    public long FileSize { get; init; }
+}

DocumentService.Application/HasZugferd/Queries/HasZugferdQuery.cs

@@ -0,0 +1,62 @@
+using DocumentService.Application.Common.Configuration;
+using DocumentService.Application.Common.DTOs;
+using DocumentService.Application.Common.Interfaces;
+using MediatR;
+using Microsoft.Extensions.Options;
+
+namespace DocumentService.Application.HasZugferd.Queries;
+
+/// <summary>
+/// Query for checking if PDF contains ZUGFeRD XML attachment
+/// </summary>
+public record HasZugferdQuery : IRequest<ZugferdCheckResult>
+{
+    /// <summary>
+    /// PDF as stream (caller is responsible for disposal)
+    /// </summary>
+    public required Stream PdfStream { get; init; }
+}
+
+/// <summary>
+/// Handler for HasZugferdQuery
+/// Checks if PDF contains ZUGFeRD/Factur-X XML attachment
+/// </summary>
+public class HasZugferdQueryHandler(
+    IPdfProcessor pdfProcessor,
+    IOptions<ZugferdSettings> settings)
+    : IRequestHandler<HasZugferdQuery, ZugferdCheckResult>
+{
+    private readonly ZugferdSettings _settings = settings.Value;
+
+    /// <summary>
+    /// Checks if PDF contains ZUGFeRD XML and returns metadata
+    /// </summary>
+    public async Task<ZugferdCheckResult> Handle(HasZugferdQuery request, CancellationToken cancellationToken)
+    {
+        // Get all attachments
+        var attachmentInfo = await pdfProcessor.CheckAttachmentsAsync(request.PdfStream);
+
+        // Check for ZUGFeRD/Factur-X XML files using configured names and patterns
+        var zugferdAttachment = attachmentInfo.Attachments.FirstOrDefault(a =>
+            _settings.ZugferdFileNames.Any(name => 
+                a.FileName.Equals(name, StringComparison.OrdinalIgnoreCase)) ||
+            _settings.ZugferdFileNamePatterns.Any(pattern => 
+                a.FileName.Contains(pattern, StringComparison.OrdinalIgnoreCase)));
+
+        if (zugferdAttachment != null)
+        {
+            return new ZugferdCheckResult
+            {
+                HasZugferd = true,
+                ZugferdFileName = zugferdAttachment.FileName,
+                ZugferdFileSize = zugferdAttachment.SizeBytes,
+                ZugferdMimeType = zugferdAttachment.MimeType
+            };
+        }
+
+        return new ZugferdCheckResult
+        {
+            HasZugferd = false
+        };
+    }
+}

DocumentService.Application/HasZugferd/Queries/HasZugferdQueryValidator.cs

@@ -0,0 +1,16 @@
+using FluentValidation;
+
+namespace DocumentService.Application.HasZugferd.Queries;
+
+/// <summary>
+/// Validator for HasZugferdQuery
+/// </summary>
+public class HasZugferdQueryValidator : AbstractValidator<HasZugferdQuery>
+{
+    public HasZugferdQueryValidator()
+    {
+        RuleFor(x => x.PdfStream)
+            .NotNull()
+            .WithMessage("PDF stream is required");
+    }
+}

DocumentService.Application/MergePdfs/MergePdfsCommand.cs

@@ -0,0 +1,53 @@
+using DocumentService.Application.Common.Interfaces;
+using FluentValidation;
+using MediatR;
+
+namespace DocumentService.Application.MergePdfs;
+
+/// <summary>
+/// Command to merge multiple PDF documents into a single PDF.
+/// </summary>
+public record MergePdfsCommand : IRequest<byte[]>
+{
+    /// <summary>
+    /// PDF streams to merge. Minimum 2 required. Each must be at Position=0.
+    /// </summary>
+    public required IReadOnlyList<Stream> PdfStreams { get; init; }
+
+    /// <summary>
+    /// Optional page ranges per PDF (null = all pages). 
+    /// Format: "1-3,5" means pages 1, 2, 3, and 5.
+    /// If provided, array length must match PdfStreams length.
+    /// </summary>
+    public IReadOnlyList<string?>? PageRanges { get; init; }
+}
+
+/// <summary>
+/// Handler for MergePdfsCommand.
+/// Delegates PDF merge operation to infrastructure layer.
+/// </summary>
+public class MergePdfsCommandHandler(IPdfProcessor pdfProcessor) 
+    : IRequestHandler<MergePdfsCommand, byte[]>
+{
+    public async Task<byte[]> Handle(MergePdfsCommand request, CancellationToken cancellationToken)
+    {
+        return await pdfProcessor.MergePdfsAsync(request.PdfStreams, request.PageRanges);
+    }
+}
+
+/// <summary>
+/// Validator for MergePdfsCommand.
+/// </summary>
+public class MergePdfsCommandValidator : AbstractValidator<MergePdfsCommand>
+{
+    public MergePdfsCommandValidator()
+    {
+        RuleFor(x => x.PdfStreams)
+            .NotNull()
+            .WithMessage("PDF streams are required");
+
+        RuleFor(x => x.PdfStreams)
+            .Must(streams => streams != null && streams.Count >= 2)
+            .WithMessage("At least 2 PDF files are required for merging");
+    }
+}

DocumentService.Application/SwissQrCode/Queries/ExtractSwissQrCodeQuery.cs

@@ -0,0 +1,44 @@
+using AutoMapper;
+using DocumentService.Application.Common.DTOs;
+using DocumentService.Application.Common.Interfaces;
+using MediatR;
+
+namespace DocumentService.Application.SwissQrCode.Queries;
+
+/// <summary>
+/// Query for extracting Swiss QR Code from PDF (Stream-based)
+/// </summary>
+public record ExtractSwissQrCodeQuery : IRequest<SwissQrCodeExtractionResult>
+{
+    /// <summary>
+    /// PDF as stream (caller is responsible for disposal)
+    /// </summary>
+    public required Stream PdfStream { get; init; }
+}
+
+/// <summary>
+/// Handler for ExtractSwissQrCodeQuery
+/// Orchestrates Swiss QR Code extraction using ISwissQrCodeProcessor and AutoMapper
+/// </summary>
+public class ExtractSwissQrCodeQueryHandler(ISwissQrCodeProcessor qrCodeProcessor, IMapper mapper) 
+    : IRequestHandler<ExtractSwissQrCodeQuery, SwissQrCodeExtractionResult>
+{
+    /// <summary>
+    /// Extracts and parses Swiss QR Code from the PDF (default: scans all pages starting with last)
+    /// Returns both parsed Bill DTO and raw QR text lines
+    /// </summary>
+    public async Task<SwissQrCodeExtractionResult> Handle(ExtractSwissQrCodeQuery request, CancellationToken cancellationToken)
+    {
+        // Extract: returns (Bill, RawLines) - pass stream directly
+        var (bill, rawLines) = await qrCodeProcessor.ExtractSwissQrCodeAsync(request.PdfStream, pageNumbers: null, cancellationToken);
+
+        // Map Codecrete Bill to DTO using AutoMapper
+        var billDto = mapper.Map<SwissQrBillDto>(bill);
+
+        // Return references (passed through) + Bill DTO + raw lines
+        return new SwissQrCodeExtractionResult(
+            Bill: billDto,
+            RawLines: rawLines
+        );
+    }
+}

DocumentService.Application/SwissQrCode/Queries/ExtractSwissQrCodeQueryValidator.cs

@@ -0,0 +1,19 @@
+using DocumentService.Application.SwissQrCode.Queries;
+using FluentValidation;
+
+namespace DocumentService.Application.SwissQrCode.Queries;
+
+/// <summary>
+/// Validates ExtractSwissQrCodeQuery before handler execution.
+/// Ensures PdfStream is not null.
+/// </summary>
+public sealed class ExtractSwissQrCodeQueryValidator : AbstractValidator<ExtractSwissQrCodeQuery>
+{
+    public ExtractSwissQrCodeQueryValidator()
+    {
+        // Rule: PdfStream must be provided
+        RuleFor(x => x.PdfStream)
+            .NotNull()
+            .WithMessage("PdfStream is required");
+    }
+}

DocumentService.Application/ValidatePdf/Queries/ValidatePdfQuery.cs

@@ -0,0 +1,28 @@
+using DocumentService.Application.Common.DTOs;
+using DocumentService.Application.Common.Interfaces;
+using MediatR;
+
+namespace DocumentService.Application.ValidatePdf.Queries;
+
+/// <summary>
+/// Query for PDF validation (Stream-based)
+/// </summary>
+public record ValidatePdfQuery : IRequest<PdfValidationResult>
+{
+    /// <summary>
+    /// PDF as stream (caller is responsible for disposal)
+    /// </summary>
+    public required Stream PdfStream { get; init; }
+}
+
+/// <summary>
+/// Handler for ValidatePdfQuery
+/// </summary>
+public class ValidatePdfQueryHandler(IPdfProcessor pdfProcessor) 
+    : IRequestHandler<ValidatePdfQuery, PdfValidationResult>
+{
+    public async Task<PdfValidationResult> Handle(ValidatePdfQuery request, CancellationToken cancellationToken)
+    {
+        return await pdfProcessor.ValidateAsync(request.PdfStream);
+    }
+}

DocumentService.Application/ValidatePdf/Queries/ValidatePdfQueryValidator.cs

@@ -0,0 +1,19 @@
+using DocumentService.Application.ValidatePdf.Queries;
+using FluentValidation;
+
+namespace DocumentService.Application.ValidatePdf.Queries;
+
+/// <summary>
+/// Validator for ValidatePdfQuery
+/// Ensures PdfStream is not null
+/// </summary>
+public class ValidatePdfQueryValidator : AbstractValidator<ValidatePdfQuery>
+{
+    public ValidatePdfQueryValidator()
+    {
+        // Rule: PdfStream must be provided
+        RuleFor(x => x.PdfStream)
+            .NotNull()
+            .WithMessage("PdfStream is required");
+    }
+}

DocumentService.Application/ValidatePdfA/Queries/ValidatePdfAQuery.cs

@@ -0,0 +1,28 @@
+using DocumentService.Application.Common.DTOs;
+using DocumentService.Application.Common.Interfaces;
+using MediatR;
+
+namespace DocumentService.Application.ValidatePdfA.Queries;
+
+/// <summary>
+/// Query for PDF/A validation (Stream-based)
+/// </summary>
+public record ValidatePdfAQuery : IRequest<PdfAValidationResult>
+{
+    /// <summary>
+    /// PDF as stream (caller is responsible for disposal)
+    /// </summary>
+    public required Stream PdfStream { get; init; }
+}
+
+/// <summary>
+/// Handler for ValidatePdfAQuery
+/// </summary>
+public class ValidatePdfAQueryHandler(IPdfProcessor pdfProcessor) 
+    : IRequestHandler<ValidatePdfAQuery, PdfAValidationResult>
+{
+    public async Task<PdfAValidationResult> Handle(ValidatePdfAQuery request, CancellationToken cancellationToken)
+    {
+        return await pdfProcessor.ValidatePdfAAsync(request.PdfStream);
+    }
+}

DocumentService.Application/ValidatePdfA/Validators/ValidatePdfAQueryValidator.cs

@@ -0,0 +1,18 @@
+using FluentValidation;
+
+namespace DocumentService.Application.ValidatePdfA.Validators;
+
+/// <summary>
+/// Validator for ValidatePdfAQuery
+/// Ensures PdfStream is not null
+/// </summary>
+public class ValidatePdfAQueryValidator : AbstractValidator<Queries.ValidatePdfAQuery>
+{
+    public ValidatePdfAQueryValidator()
+    {
+        // Rule: PdfStream must be provided
+        RuleFor(x => x.PdfStream)
+            .NotNull()
+            .WithMessage("PdfStream is required");
+    }
+}

DocumentService.Client/Client.cs

@@ -0,0 +1,95 @@
+using DocumentService.Client.Configuration;
+using DocumentService.Client.Extensions;
+using DocumentService.Client.Interfaces;
+using DocumentService.Client.Models.ValueObjects;
+using Microsoft.Extensions.DependencyInjection;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace DocumentService.Client;
+
+/// <summary>
+/// Static entry point for configuring and building the DocumentService client.
+/// </summary>
+public static class Client
+{
+    private static Action<DocumentServiceClientOptions> Options { get; set; } = null!;
+
+    private static readonly Lazy<IServiceProvider> LazyProvider = new(() =>
+    {
+        var services = new ServiceCollection();
+        services.AddDocumentServiceClients(Options);
+        return services.BuildServiceProvider();
+    });
+
+    public static bool IsConfigured => LazyProvider.IsValueCreated;
+
+    public static OnReconfigure OnReconfigure { get; set; } = OnReconfigure.ThrowException;
+
+    /// <summary>
+    /// Configures the client using a full <see cref="DocumentServiceClientOptions"/> action.
+    /// </summary>
+    /// <param name="configuration">Action that configures the client options.</param>
+    public static void Configure(Action<DocumentServiceClientOptions> configuration)
+    {
+        if(IsConfigured)
+            switch (OnReconfigure)
+            {
+                case OnReconfigure.ThrowException:
+                    throw new InvalidOperationException("DocumentService.Client is already configured. Reconfiguration is not allowed.");
+                case OnReconfigure.Ignore:
+                    return;
+            }
+        Options = configuration;
+        _ = LazyProvider.Value; // init service provider
+    }
+
+    /// <summary>
+    /// Configures the client with only a base URL. Use the overload with options action for full control.
+    /// </summary>
+    /// <param name="baseUrl">Base URL of the DocumentService API.</param>
+    public static void Configure(string baseUrl)
+    {
+        if (IsConfigured)
+            switch (OnReconfigure)
+            {
+                case OnReconfigure.ThrowException:
+                    throw new InvalidOperationException("DocumentService.Client is already configured. Reconfiguration is not allowed.");
+                case OnReconfigure.Ignore:
+                    return;
+            }
+
+        Options = options => {
+            options = new DocumentServiceClientOptions
+            {
+                BaseUrl = baseUrl
+            };
+        };
+        _ = LazyProvider.Value; // init service provider
+    }
+
+    private static IServiceProvider Provider => IsConfigured 
+        ? LazyProvider.Value 
+        : throw new InvalidOperationException("DocumentService.Client is not configured.");
+
+    private static T GetRequiredServiceOfScope<T>() where T : notnull => Provider.CreateAsyncScope().ServiceProvider.GetRequiredService<T>();
+
+    #region Controllers
+    public static IPdfAttachmentClient Attachment => GetRequiredServiceOfScope<IPdfAttachmentClient>();
+
+    public static IPdfConversionClient Conversion => GetRequiredServiceOfScope<IPdfConversionClient>();
+
+    public static IPdfOperationsClient Operations => GetRequiredServiceOfScope<IPdfOperationsClient>();
+
+    public static IPdfValidationClient Validation => GetRequiredServiceOfScope<IPdfValidationClient>();
+
+    public static ISwissQrCodeClient SwissQrCode => GetRequiredServiceOfScope<ISwissQrCodeClient>();
+
+    public static IZugferdClient Zugferd => GetRequiredServiceOfScope<IZugferdClient>();
+
+    public static IWorkflowsClient Workflows => GetRequiredServiceOfScope<IWorkflowsClient>();
+    #endregion
+}

DocumentService.Client/Clients/BaseDocumentClient.cs

@@ -0,0 +1,179 @@
+using Microsoft.Extensions.Logging;
+using System.Net.Http;
+using System.Net.Http.Headers;
+using System.Net.Http.Json;
+
+namespace DocumentService.Client.Clients;
+
+/// <summary>
+/// Base class for all DocumentService HTTP clients.
+/// Provides common HTTP operations and error handling.
+/// </summary>
+/// <remarks>
+/// 
+/// </remarks>
+/// <param name="HttpClient"></param>
+/// <param name="logger"></param>
+/// <exception cref="ArgumentNullException"></exception>
+public abstract class BaseDocumentClient(HttpClient HttpClient, ILogger logger)
+{
+    /// <summary>
+    /// 
+    /// </summary>
+    protected readonly ILogger Logger = logger ?? throw new ArgumentNullException(nameof(logger));
+
+    /// <summary>
+    /// Sends a multipart/form-data POST with a single file and deserializes the JSON response.
+    /// </summary>
+    protected async Task<TResponse?> SendMultipartAsync<TResponse>(
+        string endpoint,
+        Stream fileStream,
+        string fileName = "file.pdf",
+        CancellationToken cancellationToken = default)
+    {
+        using var content = new MultipartFormDataContent();
+        var streamContent = new StreamContent(fileStream);
+        streamContent.Headers.ContentType = new MediaTypeHeaderValue("application/pdf");
+        content.Add(streamContent, "file", fileName);
+
+        var response = await HttpClient.PostAsync(endpoint, content, cancellationToken);
+        response.EnsureSuccessStatusCode();
+
+        return await response.Content.ReadFromJsonAsync<TResponse>(cancellationToken);
+    }
+
+    /// <summary>
+    /// Sends a multipart/form-data POST with a single file and returns the response as a stream.
+    /// </summary>
+    protected async Task<Stream> SendMultipartForStreamAsync(
+        string endpoint,
+        Stream fileStream,
+        string fileName = "file.pdf",
+        CancellationToken cancellationToken = default)
+    {
+        using var content = new MultipartFormDataContent();
+        var streamContent = new StreamContent(fileStream);
+        streamContent.Headers.ContentType = new MediaTypeHeaderValue("application/pdf");
+        content.Add(streamContent, "file", fileName);
+
+        var response = await HttpClient.PostAsync(endpoint, content, cancellationToken);
+        response.EnsureSuccessStatusCode();
+
+#if NETFRAMEWORK
+        return await response.Content.ReadAsStreamAsync();
+#else
+        return await response.Content.ReadAsStreamAsync(cancellationToken);
+#endif
+    }
+
+    /// <summary>
+    /// Sends a multipart/form-data POST with a single file and returns the raw byte array.
+    /// </summary>
+    protected async Task<byte[]> SendMultipartForBinaryAsync(
+        string endpoint,
+        Stream fileStream,
+        string fileName = "file.pdf",
+        CancellationToken cancellationToken = default)
+    {
+        using var content = new MultipartFormDataContent();
+        var streamContent = new StreamContent(fileStream);
+        streamContent.Headers.ContentType = new MediaTypeHeaderValue("application/pdf");
+        content.Add(streamContent, "file", fileName);
+
+        var response = await HttpClient.PostAsync(endpoint, content, cancellationToken);
+        response.EnsureSuccessStatusCode();
+
+#if NETFRAMEWORK
+        return await response.Content.ReadAsByteArrayAsync();
+#else
+        return await response.Content.ReadAsByteArrayAsync(cancellationToken);
+#endif
+    }
+
+    /// <summary>
+    /// Sends a caller-built <see cref="MultipartFormDataContent"/> and returns the response as a stream.
+    /// Use this overload when the multipart body contains more than one file (e.g., merge).
+    /// </summary>
+    protected async Task<Stream> SendMultipartContentForStreamAsync(
+        string endpoint,
+        MultipartFormDataContent content,
+        CancellationToken cancellationToken = default)
+    {
+        var response = await HttpClient.PostAsync(endpoint, content, cancellationToken);
+        response.EnsureSuccessStatusCode();
+
+#if NETFRAMEWORK
+        return await response.Content.ReadAsStreamAsync();
+#else
+        return await response.Content.ReadAsStreamAsync(cancellationToken);
+#endif
+    }
+
+    /// <summary>
+    /// Serializes <paramref name="request"/> as JSON, POSTs it, and deserializes the response.
+    /// </summary>
+    protected async Task<TResponse?> SendJsonAsync<TRequest, TResponse>(
+        string endpoint,
+        TRequest request,
+        CancellationToken cancellationToken = default)
+    {
+        var response = await HttpClient.PostAsJsonAsync(endpoint, request, cancellationToken);
+        response.EnsureSuccessStatusCode();
+
+        return await response.Content.ReadFromJsonAsync<TResponse>(cancellationToken);
+    }
+
+    /// <summary>
+    /// Serializes <paramref name="request"/> as JSON, POSTs it, and returns the response as a stream.
+    /// </summary>
+    protected async Task<Stream> SendJsonForStreamAsync<TRequest>(
+        string endpoint,
+        TRequest request,
+        CancellationToken cancellationToken = default)
+    {
+        var response = await HttpClient.PostAsJsonAsync(endpoint, request, cancellationToken);
+        response.EnsureSuccessStatusCode();
+
+#if NETFRAMEWORK
+        return await response.Content.ReadAsStreamAsync();
+#else
+        return await response.Content.ReadAsStreamAsync(cancellationToken);
+#endif
+    }
+
+    /// <summary>
+    /// Serializes <paramref name="request"/> as JSON, POSTs it, and returns the raw byte array.
+    /// </summary>
+    protected async Task<byte[]> SendJsonForBinaryAsync<TRequest>(
+        string endpoint,
+        TRequest request,
+        CancellationToken cancellationToken = default)
+    {
+        var response = await HttpClient.PostAsJsonAsync(endpoint, request, cancellationToken);
+        response.EnsureSuccessStatusCode();
+
+#if NETFRAMEWORK
+        return await response.Content.ReadAsByteArrayAsync();
+#else
+        return await response.Content.ReadAsByteArrayAsync(cancellationToken);
+#endif
+    }
+
+    /// <summary>Converts a byte array to a Base64 string.</summary>
+    protected static string ToBase64(byte[] bytes) => Convert.ToBase64String(bytes);
+
+    /// <summary>Reads a stream fully into a byte array.</summary>
+    protected static async Task<byte[]> StreamToBytesAsync(Stream stream, CancellationToken cancellationToken = default)
+    {
+        if (stream is MemoryStream ms)
+            return ms.ToArray();
+
+        using var memoryStream = new MemoryStream();
+#if NET8_0
+        await stream.CopyToAsync(memoryStream, cancellationToken);
+#else
+        await stream.CopyToAsync(memoryStream);
+#endif
+        return memoryStream.ToArray();
+    }
+}

DocumentService.Client/Clients/PdfAttachmentClient.cs

@@ -0,0 +1,125 @@
+using DocumentService.Application.Common.DTOs;
+using DocumentService.Client.Interfaces;
+using DocumentService.Application.Common.DTOs.Requests;
+using Microsoft.Extensions.Logging;
+using System.IO.Compression;
+using System.Net.Http;
+
+namespace DocumentService.Client.Clients;
+
+/// <summary>
+/// Implementation of PDF attachment client.
+/// </summary>
+public class PdfAttachmentClient(HttpClient httpClient, ILogger<PdfAttachmentClient> logger)
+    : BaseDocumentClient(httpClient, logger), IPdfAttachmentClient
+{
+    /// <inheritdoc />
+    public async Task<AttachmentCheckResult> CheckAsync(Stream pdfStream, CancellationToken cancellationToken = default)
+    {
+        Logger.LogDebug("Checking PDF attachments from stream (multipart)");
+
+        var result = await SendMultipartAsync<AttachmentCheckResult>(
+            "/api/pdf/attachments/check",
+            pdfStream,
+            "document.pdf",
+            cancellationToken);
+
+        return result ?? throw new InvalidOperationException("API returned null response");
+    }
+
+    /// <inheritdoc />
+    public async Task<AttachmentCheckResult> CheckAsync(byte[] pdfBytes, CancellationToken cancellationToken = default)
+    {
+        Logger.LogDebug("Checking PDF attachments from byte array (Base64 JSON)");
+
+        var request = new CheckPdfAttachmentsRequest { Base64Pdf = ToBase64(pdfBytes) };
+
+        var result = await SendJsonAsync<CheckPdfAttachmentsRequest, AttachmentCheckResult>(
+            "/api/pdf/attachments/check",
+            request,
+            cancellationToken);
+
+        return result ?? throw new InvalidOperationException("API returned null response");
+    }
+
+    /// <inheritdoc />
+    public async Task<Dictionary<string, Stream>> ExtractAsync(Stream pdfStream, CancellationToken cancellationToken = default)
+    {
+        Logger.LogDebug("Extracting PDF attachments from stream (multipart)");
+
+        var zipStream = await SendMultipartForStreamAsync(
+            "/api/pdf/attachments/extract",
+            pdfStream,
+            "document.pdf",
+            cancellationToken);
+
+        return UnzipToStreams(zipStream);
+    }
+
+    /// <inheritdoc />
+    public async Task<Dictionary<string, Stream>> ExtractAsync(byte[] pdfBytes, CancellationToken cancellationToken = default)
+    {
+        Logger.LogDebug("Extracting PDF attachments from byte array (Base64 JSON)");
+
+        var request = new ExtractPdfAttachmentsRequest { Base64Pdf = ToBase64(pdfBytes) };
+
+        var zipStream = await SendJsonForStreamAsync(
+            "/api/pdf/attachments/extract",
+            request,
+            cancellationToken);
+
+        return UnzipToStreams(zipStream);
+    }
+
+    /// <inheritdoc />
+    [Obsolete("API endpoint not implemented yet")]
+    public Task<Stream> AddAsync(Stream pdfStream, List<AttachmentRequestDto> attachments, CancellationToken cancellationToken = default)
+    {
+        Logger.LogWarning("AddAttachments endpoint is not implemented yet in API");
+        throw new NotImplementedException("API endpoint /api/pdf/attachments/add is not implemented yet");
+    }
+
+    /// <inheritdoc />
+    [Obsolete("API endpoint not implemented yet")]
+    public Task<Stream> AddAsync(byte[] pdfBytes, List<AttachmentRequestDto> attachments, CancellationToken cancellationToken = default)
+    {
+        Logger.LogWarning("AddAttachments endpoint is not implemented yet in API");
+        throw new NotImplementedException("API endpoint /api/pdf/attachments/add is not implemented yet");
+    }
+
+    // ?????????????????????????????????????????????????????????????????????????
+    // Private helpers
+    // ?????????????????????????????????????????????????????????????????????????
+
+    /// <summary>
+    /// Reads a ZIP stream and returns a dictionary mapping each entry's full name
+    /// to an in-memory <see cref="MemoryStream"/> containing the decompressed bytes.
+    /// The caller owns the returned streams and is responsible for disposing them.
+    /// </summary>
+    private static Dictionary<string, Stream> UnzipToStreams(Stream zipStream)
+    {
+        var result = new Dictionary<string, Stream>(StringComparer.OrdinalIgnoreCase);
+
+        using var archive = new ZipArchive(zipStream, ZipArchiveMode.Read, leaveOpen: false);
+
+        foreach (var entry in archive.Entries)
+        {
+            // Skip directory entries (name ends with '/')
+            if (string.IsNullOrEmpty(entry.Name))
+                continue;
+
+            var ms = new MemoryStream((int)entry.Length);
+
+            using (var entryStream = entry.Open())
+            {
+                entryStream.CopyTo(ms);
+            }
+
+            ms.Position = 0;
+            result[entry.FullName] = ms;
+        }
+
+        return result;
+    }
+}
+

DocumentService.Client/Clients/PdfConversionClient.cs

@@ -0,0 +1,48 @@
+using DocumentService.Client.Interfaces;
+using DocumentService.Application.Common.DTOs.Requests;
+using Microsoft.Extensions.Logging;
+using System.Net.Http;
+
+namespace DocumentService.Client.Clients;
+
+/// <summary>
+/// Implementation of PDF conversion client (PDF ? PDF/A).
+/// </summary>
+/// <remarks>
+/// All methods throw <see cref="NotImplementedException"/> because the corresponding
+/// API endpoints are not yet implemented on the server side.
+/// </remarks>
+public class PdfConversionClient(HttpClient httpClient, ILogger<PdfConversionClient> logger) : BaseDocumentClient(httpClient, logger), IPdfConversionClient
+{
+    /// <inheritdoc />
+    [Obsolete("API endpoint not implemented yet")]
+    public Task<Stream> ToPdfAAsync(Stream pdfStream, string pdfALevel = "PDF/A-3b", CancellationToken cancellationToken = default)
+    {
+        Logger.LogWarning("ConvertToPdfA endpoint is not implemented yet in API");
+        throw new NotImplementedException("API endpoint POST /api/pdf/conversion/to-pdfa is not implemented yet");
+    }
+
+    /// <inheritdoc />
+    [Obsolete("API endpoint not implemented yet")]
+    public Task<Stream> ToPdfAAsync(byte[] pdfBytes, string pdfALevel = "PDF/A-3b", CancellationToken cancellationToken = default)
+    {
+        Logger.LogWarning("ConvertToPdfA endpoint is not implemented yet in API");
+        throw new NotImplementedException("API endpoint POST /api/pdf/conversion/to-pdfa is not implemented yet");
+    }
+
+    /// <inheritdoc />
+    [Obsolete("API endpoint not implemented yet")]
+    public Task<Stream> FromPdfAAsync(Stream pdfStream, CancellationToken cancellationToken = default)
+    {
+        Logger.LogWarning("ConvertFromPdfA endpoint is not implemented yet in API");
+        throw new NotImplementedException("API endpoint POST /api/pdf/conversion/from-pdfa is not implemented yet");
+    }
+
+    /// <inheritdoc />
+    [Obsolete("API endpoint not implemented yet")]
+    public Task<Stream> FromPdfAAsync(byte[] pdfBytes, CancellationToken cancellationToken = default)
+    {
+        Logger.LogWarning("ConvertFromPdfA endpoint is not implemented yet in API");
+        throw new NotImplementedException("API endpoint POST /api/pdf/conversion/from-pdfa is not implemented yet");
+    }
+}

DocumentService.Client/Clients/PdfOperationsClient.cs

@@ -0,0 +1,161 @@
+using DocumentService.Client.Interfaces;
+using DocumentService.Application.Common.DTOs.Requests;
+using Microsoft.Extensions.Logging;
+using System.Net.Http;
+using System.Net.Http.Headers;
+
+namespace DocumentService.Client.Clients;
+
+/// <summary>
+/// Implementation of PDF operations client (merge, annotate, stamp).
+/// </summary>
+public class PdfOperationsClient(HttpClient httpClient, ILogger<PdfOperationsClient> logger) : BaseDocumentClient(httpClient, logger), IPdfOperationsClient
+{
+
+    // ==================== MERGE OPERATIONS ====================
+
+    /// <inheritdoc />
+    public async Task<Stream> MergeAsync(IEnumerable<Stream> pdfStreams, List<string?>? pageRanges = null, CancellationToken cancellationToken = default)
+    {
+        using var content = new MultipartFormDataContent();
+
+        foreach (var stream in pdfStreams)
+        {
+            var streamContent = new StreamContent(stream);
+            streamContent.Headers.ContentType = new MediaTypeHeaderValue("application/pdf");
+            content.Add(streamContent, "files", $"file_{Guid.NewGuid()}.pdf");
+        }
+
+        return await SendMultipartContentForStreamAsync("/api/pdf/operations/merge", content, cancellationToken);
+    }
+
+    /// <inheritdoc />
+    public async Task<Stream> MergeAsync(IEnumerable<byte[]> pdfByteArrays, List<string?>? pageRanges = null, CancellationToken cancellationToken = default)
+    {
+        var request = new MergePdfsBase64Request
+        {
+            Base64Pdfs = [.. pdfByteArrays.Select(ToBase64)],
+            PageRanges = pageRanges
+        };
+
+        return await SendJsonForStreamAsync(
+            "/api/pdf/operations/merge",
+            request,
+            cancellationToken);
+    }
+
+    // ==================== ANNOTATION OPERATIONS ====================
+
+    /// <inheritdoc />
+    public async Task<Stream> AnnotateAsync(Stream pdfStream, AddAnnotationBase64Request request, CancellationToken cancellationToken = default)
+    {
+        // For multipart, we need to send form data with all annotation parameters
+        using var content = new MultipartFormDataContent();
+        
+        var streamContent = new StreamContent(pdfStream);
+        streamContent.Headers.ContentType = new MediaTypeHeaderValue("application/pdf");
+        content.Add(streamContent, "File", "document.pdf");
+
+        // Add annotation parameters as form fields
+        content.Add(new StringContent(request.AnnotationType.ToString()), "AnnotationType");
+        content.Add(new StringContent(request.PageNumber.ToString()), "PageNumber");
+        content.Add(new StringContent(request.X1.ToString()), "X1");
+        content.Add(new StringContent(request.Y1.ToString()), "Y1");
+        
+        if (request.X2.HasValue)
+            content.Add(new StringContent(request.X2.Value.ToString()), "X2");
+        if (request.Y2.HasValue)
+            content.Add(new StringContent(request.Y2.Value.ToString()), "Y2");
+        if (request.Width.HasValue)
+            content.Add(new StringContent(request.Width.Value.ToString()), "Width");
+        if (request.Height.HasValue)
+            content.Add(new StringContent(request.Height.Value.ToString()), "Height");
+        if (!string.IsNullOrEmpty(request.Content))
+            content.Add(new StringContent(request.Content), "Content");
+        if (!string.IsNullOrEmpty(request.Author))
+            content.Add(new StringContent(request.Author), "Author");
+        if (!string.IsNullOrEmpty(request.Color))
+            content.Add(new StringContent(request.Color), "Color");
+        if (request.TextMarkupStyle.HasValue)
+            content.Add(new StringContent(request.TextMarkupStyle.Value.ToString()), "TextMarkupStyle");
+        
+        content.Add(new StringContent(request.Origin.ToString()), "Origin");
+
+        return await SendMultipartContentForStreamAsync("/api/pdf/operations/annotate", content, cancellationToken);
+    }
+
+    /// <inheritdoc />
+    public async Task<Stream> AnnotateAsync(byte[] pdfBytes, AddAnnotationBase64Request request, CancellationToken cancellationToken = default)
+    {
+        var requestWithPdf = request with { Base64Pdf = ToBase64(pdfBytes) };
+
+        return await SendJsonForStreamAsync(
+            "/api/pdf/operations/annotate",
+            requestWithPdf,
+            cancellationToken);
+    }
+
+    // ==================== STAMP OPERATIONS ====================
+
+    /// <inheritdoc />
+    public async Task<Stream> StampAsync(Stream pdfStream, AddStampBase64Request request, CancellationToken cancellationToken = default)
+    {
+        // For multipart, we need to send form data with all stamp parameters
+        using var content = new MultipartFormDataContent();
+        
+        var streamContent = new StreamContent(pdfStream);
+        streamContent.Headers.ContentType = new MediaTypeHeaderValue("application/pdf");
+        content.Add(streamContent, "File", "document.pdf");
+
+        // Add stamp parameters as form fields
+        content.Add(new StringContent(request.StampType.ToString()), "StampType");
+        content.Add(new StringContent(request.X.ToString()), "X");
+        content.Add(new StringContent(request.Y.ToString()), "Y");
+        
+        if (request.PageNumbers != null && request.PageNumbers.Length > 0)
+        {
+            foreach (var pageNum in request.PageNumbers)
+            {
+                content.Add(new StringContent(pageNum.ToString()), "PageNumbers");
+            }
+        }
+
+        if (request.Width.HasValue)
+            content.Add(new StringContent(request.Width.Value.ToString()), "Width");
+        if (request.Height.HasValue)
+            content.Add(new StringContent(request.Height.Value.ToString()), "Height");
+        
+        content.Add(new StringContent(request.Origin.ToString()), "Origin");
+        
+        if (!string.IsNullOrEmpty(request.Text))
+            content.Add(new StringContent(request.Text), "Text");
+        if (!string.IsNullOrEmpty(request.FontName))
+            content.Add(new StringContent(request.FontName), "FontName");
+        if (request.FontSize.HasValue)
+            content.Add(new StringContent(request.FontSize.Value.ToString()), "FontSize");
+        if (!string.IsNullOrEmpty(request.Color))
+            content.Add(new StringContent(request.Color), "Color");
+        if (request.Opacity.HasValue)
+            content.Add(new StringContent(request.Opacity.Value.ToString()), "Opacity");
+        if (request.Rotation.HasValue)
+            content.Add(new StringContent(request.Rotation.Value.ToString()), "Rotation");
+        
+        content.Add(new StringContent(request.Placement.ToString()), "Placement");
+        
+        if (request.PredefinedType.HasValue)
+            content.Add(new StringContent(request.PredefinedType.Value.ToString()), "PredefinedType");
+
+        return await SendMultipartContentForStreamAsync("/api/pdf/operations/stamp", content, cancellationToken);
+    }
+
+    /// <inheritdoc />
+    public async Task<Stream> StampAsync(byte[] pdfBytes, AddStampBase64Request request, CancellationToken cancellationToken = default)
+    {
+        var requestWithPdf = request with { Base64Pdf = ToBase64(pdfBytes) };
+
+        return await SendJsonForStreamAsync(
+            "/api/pdf/operations/stamp",
+            requestWithPdf,
+            cancellationToken);
+    }
+}

DocumentService.Client/Clients/PdfValidationClient.cs

@@ -0,0 +1,69 @@
+using DocumentService.Application.Common.DTOs;
+using DocumentService.Client.Interfaces;
+using DocumentService.Application.Common.DTOs.Requests;
+using Microsoft.Extensions.Logging;
+using System.Net.Http;
+
+namespace DocumentService.Client.Clients;
+
+/// <summary>
+/// Implementation of PDF validation client.
+/// </summary>
+public class PdfValidationClient(HttpClient httpClient, ILogger<PdfValidationClient> logger) : BaseDocumentClient(httpClient, logger), IPdfValidationClient
+{
+    /// <inheritdoc />
+    public async Task<PdfValidationResult> ValidateAsync(Stream pdfStream, CancellationToken cancellationToken = default)
+    {
+        var result = await SendMultipartAsync<PdfValidationResult>(
+            "/api/pdf/validation/validate",
+            pdfStream,
+            "document.pdf",
+            cancellationToken);
+
+        return result ?? throw new InvalidOperationException("API returned null response");
+    }
+
+    /// <inheritdoc />
+    public async Task<PdfValidationResult> ValidateAsync(byte[] pdfBytes, CancellationToken cancellationToken = default)
+    {
+        var request = new ValidatePdfBase64Request
+        {
+            Base64Pdf = ToBase64(pdfBytes)
+        };
+
+        var result = await SendJsonAsync<ValidatePdfBase64Request, PdfValidationResult>(
+            "/api/pdf/validation/validate",
+            request,
+            cancellationToken);
+
+        return result ?? throw new InvalidOperationException("API returned null response");
+    }
+
+    /// <inheritdoc />
+    public async Task<PdfAValidationResult> ValidatePdfAAsync(Stream pdfStream, CancellationToken cancellationToken = default)
+    {
+        var result = await SendMultipartAsync<PdfAValidationResult>(
+            "/api/pdf/validation/validate-pdfa",
+            pdfStream,
+            "document.pdf",
+            cancellationToken);
+
+        return result ?? throw new InvalidOperationException("API returned null response");
+    }
+
+    /// <inheritdoc />
+    public async Task<PdfAValidationResult> ValidatePdfAAsync(byte[] pdfBytes, CancellationToken cancellationToken = default)
+    {
+        var request = new ValidatePdfABase64Request
+        {
+            Base64Pdf = ToBase64(pdfBytes)
+        };
+
+        var result = await SendJsonAsync<ValidatePdfABase64Request, PdfAValidationResult>(
+            "/api/pdf/validation/validate-pdfa",
+            request,
+            cancellationToken);
+
+        return result ?? throw new InvalidOperationException("API returned null response");
+    }
+}

DocumentService.Client/Clients/SwissQrCodeClient.cs

@@ -0,0 +1,45 @@
+using DocumentService.Application.Common.DTOs;
+using DocumentService.Client.Interfaces;
+using DocumentService.Application.Common.DTOs.Requests;
+using Microsoft.Extensions.Logging;
+using System.Net.Http;
+
+namespace DocumentService.Client.Clients;
+
+/// <summary>
+/// Implementation of Swiss QR Code extraction client.
+/// </summary>
+public class SwissQrCodeClient(HttpClient httpClient, ILogger<SwissQrCodeClient> logger) : BaseDocumentClient(httpClient, logger), ISwissQrCodeClient
+{
+    /// <inheritdoc />
+    public async Task<SwissQrCodeExtractionResult> ExtractAsync(Stream pdfStream, bool raw = false, CancellationToken cancellationToken = default)
+    {
+        var endpoint = $"/api/pdf/qr-code/extract-swiss?raw={raw}";
+
+        var result = await SendMultipartAsync<SwissQrCodeExtractionResult>(
+            endpoint,
+            pdfStream,
+            "document.pdf",
+            cancellationToken);
+
+        return result ?? throw new InvalidOperationException("API returned null response");
+    }
+
+    /// <inheritdoc />
+    public async Task<SwissQrCodeExtractionResult> ExtractAsync(byte[] pdfBytes, bool raw = false, CancellationToken cancellationToken = default)
+    {
+        var endpoint = $"/api/pdf/qr-code/extract-swiss?raw={raw}";
+
+        var request = new ExtractSwissQrCodeBase64Request
+        {
+            Base64Pdf = ToBase64(pdfBytes)
+        };
+
+        var result = await SendJsonAsync<ExtractSwissQrCodeBase64Request, SwissQrCodeExtractionResult>(
+            endpoint,
+            request,
+            cancellationToken);
+
+        return result ?? throw new InvalidOperationException("API returned null response");
+    }
+}

DocumentService.Client/Clients/WorkflowsClient.cs

@@ -0,0 +1,44 @@
+using DocumentService.Application.Common.DTOs;
+using DocumentService.Client.Interfaces;
+using DocumentService.Client.Models.Results;
+
+namespace DocumentService.Client.Clients;
+
+/// <summary>
+/// Orchestrated multi-step workflows that compose multiple DocumentService clients
+/// into single, higher-level operations.
+/// </summary>
+public class WorkflowsClient(IPdfValidationClient validation, ISwissQrCodeClient swissQrCode) : IWorkflowsClient
+{
+    /// <inheritdoc />
+    public async Task<SwissQrCodeResult> InspectSwissQrCodeAsync(
+        byte[] pdfBytes,
+        bool raw = false,
+        CancellationToken cancellationToken = default)
+    {
+        var validationResult = await validation.ValidateAsync(pdfBytes, cancellationToken);
+        var qrCode = validationResult.IsValid
+            ? await swissQrCode.ExtractAsync(pdfBytes, raw, cancellationToken)
+            : null;
+        return new SwissQrCodeResult(qrCode, validationResult);
+    }
+
+    /// <inheritdoc />
+    public async Task<SwissQrCodeResult> InspectSwissQrCodeAsync(
+        Stream pdfStream,
+        bool raw = false,
+        CancellationToken cancellationToken = default)
+    {
+        var validationResult = await validation.ValidateAsync(pdfStream, cancellationToken);
+
+        if (!validationResult.IsValid)
+            return new SwissQrCodeResult(null, validationResult);
+
+        // Stream was consumed by validation – reset if possible, otherwise re-open is caller's responsibility.
+        if (pdfStream.CanSeek)
+            pdfStream.Position = 0;
+
+        var qrCode = await swissQrCode.ExtractAsync(pdfStream, raw, cancellationToken);
+        return new SwissQrCodeResult(qrCode, validationResult);
+    }
+}

DocumentService.Client/Clients/ZugferdClient.cs

@@ -0,0 +1,89 @@
+using DocumentService.Application.Common.DTOs;
+using DocumentService.Application.ExtractZugferd;
+using DocumentService.Client.Interfaces;
+using DocumentService.Application.Common.DTOs.Requests;
+using Microsoft.Extensions.Logging;
+using System.Net.Http;
+
+namespace DocumentService.Client.Clients;
+
+/// <summary>
+/// Implementation of ZUGFeRD client (detection and extraction).
+/// </summary>
+public class ZugferdClient(HttpClient httpClient, ILogger<ZugferdClient> logger) : BaseDocumentClient(httpClient, logger), IZugferdClient
+{
+    /// <inheritdoc />
+    public async Task<ZugferdCheckResult> CheckAsync(Stream pdfStream, CancellationToken cancellationToken = default)
+    {
+        var result = await SendMultipartAsync<ZugferdCheckResult>(
+            "/api/pdf/zugferd/has-zugferd",
+            pdfStream,
+            "document.pdf",
+            cancellationToken);
+
+        return result ?? throw new InvalidOperationException("API returned null response");
+    }
+
+    /// <inheritdoc />
+    public async Task<ZugferdCheckResult> CheckAsync(byte[] pdfBytes, CancellationToken cancellationToken = default)
+    {
+        var request = new HasZugferdRequest { Base64Pdf = ToBase64(pdfBytes) };
+
+        var result = await SendJsonAsync<HasZugferdRequest, ZugferdCheckResult>(
+            "/api/pdf/zugferd/has-zugferd",
+            request,
+            cancellationToken);
+
+        return result ?? throw new InvalidOperationException("API returned null response");
+    }
+
+    /// <inheritdoc />
+    public async Task<Stream> ExtractAsync(Stream pdfStream, CancellationToken cancellationToken = default)
+    {
+        // asFile=true returns the XML file directly (application/xml stream)
+        return await SendMultipartForStreamAsync(
+            "/api/pdf/zugferd/extract?asFile=true",
+            pdfStream,
+            "document.pdf",
+            cancellationToken);
+    }
+
+    /// <inheritdoc />
+    public async Task<Stream> ExtractAsync(byte[] pdfBytes, CancellationToken cancellationToken = default)
+    {
+        var request = new ExtractZugferdRequest { Base64Pdf = ToBase64(pdfBytes) };
+
+        // format=file returns the XML file directly (application/xml stream)
+        return await SendJsonForStreamAsync(
+            "/api/pdf/zugferd/extract?format=file",
+            request,
+            cancellationToken);
+    }
+
+    /// <inheritdoc />
+    public async Task<ZugferdExtractionResult> ExtractAsResultAsync(Stream pdfStream, CancellationToken cancellationToken = default)
+    {
+        // asFile=false returns JSON with metadata + XML content
+        var result = await SendMultipartAsync<ZugferdExtractionResult>(
+            "/api/pdf/zugferd/extract?asFile=false",
+            pdfStream,
+            "document.pdf",
+            cancellationToken);
+
+        return result ?? throw new InvalidOperationException("API returned null response");
+    }
+
+    /// <inheritdoc />
+    public async Task<ZugferdExtractionResult> ExtractAsResultAsync(byte[] pdfBytes, CancellationToken cancellationToken = default)
+    {
+        var request = new ExtractZugferdRequest { Base64Pdf = ToBase64(pdfBytes) };
+
+        // format=json returns JSON with metadata + XML content
+        var result = await SendJsonAsync<ExtractZugferdRequest, ZugferdExtractionResult>(
+            "/api/pdf/zugferd/extract?format=json",
+            request,
+            cancellationToken);
+
+        return result ?? throw new InvalidOperationException("API returned null response");
+    }
+}

DocumentService.Client/Configuration/DocumentServiceClientOptions.cs

@@ -0,0 +1,29 @@
+namespace DocumentService.Client.Configuration;
+
+/// <summary>
+/// Configuration options for DocumentService HTTP client.
+/// </summary>
+public class DocumentServiceClientOptions
+{
+    /// <summary>
+    /// Base URL of the DocumentService API.
+    /// </summary>
+    /// <example>https://api.example.com</example>
+    public string BaseUrl { get; set; } = "http://localhost:5000";
+
+    /// <summary>
+    /// HTTP request timeout duration.
+    /// </summary>
+    public TimeSpan Timeout { get; set; } = TimeSpan.FromMinutes(5);
+
+    /// <summary>
+    /// Maximum number of retry attempts for failed requests.
+    /// </summary>
+    public int MaxRetries { get; set; } = 3;
+
+    /// <summary>
+    /// Whether to throw exceptions on HTTP error responses (4xx, 5xx).
+    /// If false, returns null/default values instead.
+    /// </summary>
+    public bool ThrowOnError { get; set; } = true;
+}

DocumentService.Client/DocumentService.Client.csproj

@@ -0,0 +1,77 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+	<PropertyGroup>
+		<TargetFrameworks>net462;net480;net8.0</TargetFrameworks>
+		<DocumentationFile>bin\$(Configuration)\$(TargetFramework)\$(MSBuildProjectName).xml</DocumentationFile>
+		<PackageId>DocumentService.Client</PackageId>
+		<Authors>Digital Data GmbH</Authors>
+		<Company>Digital Data GmbH</Company>
+		<Product>DocumentService.Client</Product>
+		<Copyright>Copyright 2026</Copyright>
+		<PackageIcon>icon.png</PackageIcon>
+		<RepositoryUrl>http://git.dd:3000/AppStd/Rec.git</RepositoryUrl>
+		<PackageTags>digital data document service api client</PackageTags>
+		<Version>1.2.2</Version>
+		<AssemblyVersion>1.2.2.0</AssemblyVersion>
+		<FileVersion>1.2.2.0</FileVersion>
+		<Description></Description>
+		<ImplicitUsings>enable</ImplicitUsings>
+		<Nullable>enable</Nullable>
+		<LangVersion>latest</LangVersion>
+	</PropertyGroup>
+
+	<ItemGroup Condition="'$(TargetFramework)' == 'net462' Or '$(TargetFramework)' == 'net480'">
+		<Reference Include="System.IO.Compression" />
+		<Reference Include="System.IO.Compression.FileSystem" />
+	</ItemGroup>
+
+	<ItemGroup>
+		<PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="10.0.10" />
+		<PackageReference Include="Microsoft.Extensions.Logging" Version="10.0.10" />
+		<PackageReference Include="Microsoft.Extensions.Http" Version="8.0.0" />
+		<PackageReference Include="System.Net.Http.Json" Version="8.0.0" />
+		<PackageReference Include="PolySharp" Version="1.14.1">
+			<PrivateAssets>all</PrivateAssets>
+			<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+		</PackageReference>
+	</ItemGroup>
+	
+	<ItemGroup>
+		<None Include="..\assets\icon.png">
+			<Pack>True</Pack>
+			<PackagePath>\</PackagePath>
+		</None>
+	</ItemGroup>
+	
+	<ItemGroup>
+	  <ProjectReference Include="..\DocumentService.Application\DocumentService.Application.csproj">
+	    <PrivateAssets>all</PrivateAssets>
+	  </ProjectReference>
+	  <ProjectReference Include="..\DocumentService.Domain\DocumentService.Domain.csproj">
+	    <PrivateAssets>all</PrivateAssets>
+	  </ProjectReference>
+	</ItemGroup>
+
+	<!-- Embed Application and Domain DLLs into the NuGet package lib folder -->
+	<Target Name="IncludeReferencedProjectDlls" BeforeTargets="_GetPackageFiles" Condition="'$(TargetFramework)' != ''">
+	  <ItemGroup>
+	    <None Include="..\DocumentService.Application\bin\$(Configuration)\$(TargetFramework)\DocumentService.Application.dll"
+	          Pack="true" PackagePath="lib\$(TargetFramework)\" Visible="false" />
+	    <None Include="..\DocumentService.Domain\bin\$(Configuration)\$(TargetFramework)\DocumentService.Domain.dll"
+	          Pack="true" PackagePath="lib\$(TargetFramework)\" Visible="false" />
+	  </ItemGroup>
+	</Target>
+
+	<!-- Trigger inner build per-TFM to pick up IncludeReferencedProjectDlls target -->
+	<PropertyGroup>
+	  <TargetsForTfmSpecificBuildOutput>$(TargetsForTfmSpecificBuildOutput);CopyProjectReferencesToPackage</TargetsForTfmSpecificBuildOutput>
+	</PropertyGroup>
+
+	<Target Name="CopyProjectReferencesToPackage" DependsOnTargets="ResolveReferences">
+	  <ItemGroup>
+	    <BuildOutputInPackage Include="@(ReferenceCopyLocalPaths->WithMetadataValue('ReferenceSourceTarget','ProjectReference'))"
+	                          Condition="'%(Filename)' == 'DocumentService.Application' Or '%(Filename)' == 'DocumentService.Domain'" />
+	  </ItemGroup>
+	</Target>
+
+</Project>

DocumentService.Client/Extensions/ServiceCollectionExtensions.cs

@@ -0,0 +1,67 @@
+using DocumentService.Client.Clients;
+using DocumentService.Client.Configuration;
+using DocumentService.Client.Interfaces;
+using Microsoft.Extensions.DependencyInjection;
+using System.Net;
+using System.Net.Http;
+
+namespace DocumentService.Client.Extensions;
+
+/// <summary>
+/// Extension methods for registering DocumentService clients in DI container.
+/// </summary>
+public static class ServiceCollectionExtensions
+{
+    /// <summary>
+    /// Registers all six DocumentService HTTP clients as Scoped via HttpClientFactory.
+    /// </summary>
+    /// <param name="services">Service collection</param>
+    /// <param name="configureOptions">Configuration action for client options</param>
+    /// <returns>Service collection for chaining</returns>
+    public static IServiceCollection AddDocumentServiceClients(
+        this IServiceCollection services,
+        Action<DocumentServiceClientOptions> configureOptions)
+    {
+        services.Configure(configureOptions);
+
+        var options = new DocumentServiceClientOptions();
+        configureOptions(options);
+
+        var configureHandler = () => new HttpClientHandler
+        {
+            AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate
+        };
+
+        void ConfigureClient(System.Net.Http.HttpClient client)
+        {
+            client.BaseAddress = new Uri(options.BaseUrl);
+            client.Timeout = options.Timeout;
+        }
+
+        services.AddHttpClient<IPdfValidationClient, PdfValidationClient>(ConfigureClient)
+            .ConfigurePrimaryHttpMessageHandler(configureHandler);
+
+        services.AddHttpClient<IPdfAttachmentClient, PdfAttachmentClient>(ConfigureClient)
+            .ConfigurePrimaryHttpMessageHandler(configureHandler);
+
+        services.AddHttpClient<IPdfOperationsClient, PdfOperationsClient>(ConfigureClient)
+            .ConfigurePrimaryHttpMessageHandler(configureHandler);
+
+        services.AddHttpClient<ISwissQrCodeClient, SwissQrCodeClient>(ConfigureClient)
+            .ConfigurePrimaryHttpMessageHandler(configureHandler);
+
+        services.AddHttpClient<IZugferdClient, ZugferdClient>(ConfigureClient)
+            .ConfigurePrimaryHttpMessageHandler(configureHandler);
+
+        // Conversion client is registered but all methods throw NotImplementedException
+        // until the server-side endpoints are ready.
+        services.AddHttpClient<IPdfConversionClient, PdfConversionClient>(ConfigureClient)
+            .ConfigurePrimaryHttpMessageHandler(configureHandler);
+
+        // WorkflowsClient composes existing clients – no HttpClient needed.
+        services.AddScoped<IWorkflowsClient, WorkflowsClient>();
+
+        return services;
+    }
+}
+

DocumentService.Client/Extensions/StreamExtensions.cs

@@ -0,0 +1,64 @@
+using System.IO;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace DocumentService.Client.Extensions;
+
+/// <summary>
+/// Extension methods for Stream operations.
+/// </summary>
+public static class StreamExtensions
+{
+    /// <summary>
+    /// Converts a stream to a Base64-encoded string.
+    /// </summary>
+    /// <param name="stream">Source stream</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>Base64-encoded string</returns>
+    public static async Task<string> ToBase64StringAsync(this Stream stream, CancellationToken cancellationToken = default)
+    {
+        if (stream == null)
+            throw new ArgumentNullException(nameof(stream));
+
+        byte[] bytes = await stream.ToBytesAsync(cancellationToken);
+        return Convert.ToBase64String(bytes);
+    }
+
+    /// <summary>
+    /// Converts a stream to a byte array.
+    /// </summary>
+    /// <param name="stream">Source stream</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>Byte array</returns>
+    public static async Task<byte[]> ToBytesAsync(this Stream stream, CancellationToken cancellationToken = default)
+    {
+        if (stream == null)
+            throw new ArgumentNullException(nameof(stream));
+
+        if (stream is MemoryStream ms)
+        {
+            return ms.ToArray();
+        }
+
+        using var memoryStream = new MemoryStream();
+#if NET8_0
+        await stream.CopyToAsync(memoryStream, cancellationToken);
+#else
+        await stream.CopyToAsync(memoryStream);
+#endif
+        return memoryStream.ToArray();
+    }
+
+    /// <summary>
+    /// Resets stream position to beginning if seekable.
+    /// </summary>
+    /// <param name="stream">Stream to reset</param>
+    /// <returns>The same stream (for chaining)</returns>
+    public static Stream Reset(this Stream stream)
+    {
+        if (stream != null && stream.CanSeek)
+            stream.Position = 0;
+
+        return stream!;
+    }
+}

DocumentService.Client/Interfaces/IPdfAttachmentClient.cs

@@ -0,0 +1,64 @@
+using DocumentService.Application.Common.DTOs;
+using DocumentService.Application.Common.DTOs.Requests;
+
+namespace DocumentService.Client.Interfaces;
+
+/// <summary>
+/// Client for PDF attachment operations (check, extract, add).
+/// </summary>
+public interface IPdfAttachmentClient
+{
+    /// <summary>
+    /// Checks if PDF contains attachments (multipart).
+    /// </summary>
+    /// <param name="pdfStream">PDF file stream</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>Attachment check result with metadata</returns>
+    Task<AttachmentCheckResult> CheckAsync(Stream pdfStream, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Checks if PDF contains attachments (Base64).
+    /// </summary>
+    /// <param name="pdfBytes">PDF file as byte array</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>Attachment check result with metadata</returns>
+    Task<AttachmentCheckResult> CheckAsync(byte[] pdfBytes, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Extracts all embedded attachments from a PDF (multipart).
+    /// The returned dictionary maps each file name to its decompressed content stream.
+    /// </summary>
+    /// <param name="pdfStream">PDF file stream</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>Dictionary of file name ? content stream for each extracted attachment</returns>
+    Task<Dictionary<string, Stream>> ExtractAsync(Stream pdfStream, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Extracts all embedded attachments from a PDF (Base64).
+    /// The returned dictionary maps each file name to its decompressed content stream.
+    /// </summary>
+    /// <param name="pdfBytes">PDF file as byte array</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>Dictionary of file name ? content stream for each extracted attachment</returns>
+    Task<Dictionary<string, Stream>> ExtractAsync(byte[] pdfBytes, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Adds attachments to PDF (multipart). ?? Not implemented yet in API.
+    /// </summary>
+    /// <param name="pdfStream">PDF file stream</param>
+    /// <param name="attachments">Attachments to add</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>Modified PDF as stream</returns>
+    [Obsolete("API endpoint not implemented yet")]
+    Task<Stream> AddAsync(Stream pdfStream, List<AttachmentRequestDto> attachments, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Adds attachments to PDF (Base64). ?? Not implemented yet in API.
+    /// </summary>
+    /// <param name="pdfBytes">PDF file as byte array</param>
+    /// <param name="attachments">Attachments to add</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>Modified PDF as stream</returns>
+    [Obsolete("API endpoint not implemented yet")]
+    Task<Stream> AddAsync(byte[] pdfBytes, List<AttachmentRequestDto> attachments, CancellationToken cancellationToken = default);
+}