diff --git a/EnvelopeGenerator.Application/Common/Dto/PdfSignOptionsDto.cs b/EnvelopeGenerator.Application/Common/Dto/PdfSignOptionsDto.cs
index 6ec8fa26..9b9ccf60 100644
--- a/EnvelopeGenerator.Application/Common/Dto/PdfSignOptionsDto.cs
+++ b/EnvelopeGenerator.Application/Common/Dto/PdfSignOptionsDto.cs
@@ -2,15 +2,53 @@ using EnvelopeGenerator.Application.Common.Enums;
 
 namespace EnvelopeGenerator.Application.Common.Dto;
 
+/// <summary>
+/// 
+/// </summary>
 public sealed record PdfSignOptionsDto
 {
-    public string? UUID { get; set; }
-    public string? Name { get; set; }
-    public string? Reason { get; set; }
-    public string? Location { get; set; }
-    public string? Email { get; set; }
-    public string? Phone { get; set; }
-    public string? ApplicationName { get; set; }
-    public PdfSignatureCertificationLevel? CertificationLevel { get; set; }
-    public PdfVisualSignatureOptionsDto? VisualSignature { get; set; }
+    /// <summary>
+    /// 
+    /// </summary>
+    public string UUID { get; set; } = null!;
+
+    /// <summary>
+    /// 
+    /// </summary>
+    public string Name { get; set; } = null!;
+
+    /// <summary>
+    /// 
+    /// </summary>
+    public string Reason { get; set; } = null!;
+
+    /// <summary>
+    /// 
+    /// </summary>
+    public string Location { get; set; } = null!;
+
+    /// <summary>
+    /// 
+    /// </summary>
+    public string Email { get; set; } = null!;
+
+    /// <summary>
+    /// 
+    /// </summary>
+    public string Phone { get; set; } = null!;
+
+    /// <summary>
+    /// 
+    /// </summary>
+    public string ApplicationName { get; set; } = null!;
+
+    /// <summary>
+    /// 
+    /// </summary>
+    public PdfSignatureCertificationLevel CertificationLevel { get; set; }
+
+    /// <summary>
+    /// 
+    /// </summary>
+    public PdfVisualSignatureOptionsDto VisualSignature { get; set; } = null!;
 }
diff --git a/EnvelopeGenerator.Application/Common/Dto/PdfVisualSignatureOptionsDto.cs b/EnvelopeGenerator.Application/Common/Dto/PdfVisualSignatureOptionsDto.cs
index 68591c13..4716c1bb 100644
--- a/EnvelopeGenerator.Application/Common/Dto/PdfVisualSignatureOptionsDto.cs
+++ b/EnvelopeGenerator.Application/Common/Dto/PdfVisualSignatureOptionsDto.cs
@@ -1,5 +1,15 @@
 namespace EnvelopeGenerator.Application.Common.Dto;
 
+/// <summary>
+/// 
+/// </summary>
+/// <param name="ImageBytes"></param>
+/// <param name="PageNumber"></param>
+/// <param name="Left"></param>
+/// <param name="Bottom"></param>
+/// <param name="Width"></param>
+/// <param name="Height"></param>
+/// <param name="ShowLabels"></param>
 public sealed record PdfVisualSignatureOptionsDto(
     byte[] ImageBytes,
     int PageNumber,
diff --git a/EnvelopeGenerator.Infrastructure.Crypt/Services/PdfDigitalSignatureService.cs b/EnvelopeGenerator.Infrastructure.Crypt/Services/PdfDigitalSignatureService.cs
index c3b97ad4..8aa933b0 100644
--- a/EnvelopeGenerator.Infrastructure.Crypt/Services/PdfDigitalSignatureService.cs
+++ b/EnvelopeGenerator.Infrastructure.Crypt/Services/PdfDigitalSignatureService.cs
@@ -18,10 +18,8 @@ public sealed class PdfDigitalSignatureService(IOptions<Pkcs11Options> options)
 {
     private static readonly Regex SignatureReasonMetaRegex = new(@"\|\s*SFMETA:v1;doc=(?<doc>[0-9a-fA-F-]{36});sha256=(?<sha>[A-Fa-f0-9]{64})$", RegexOptions.CultureInvariant | RegexOptions.Compiled);
 
-    public async Task SignPdfAsync(Stream inputPdf, Stream outputPdf, PdfSignOptionsDto? optionsModel = null, CancellationToken cancellationToken = default)
+    public async Task SignPdfAsync(Stream inputPdf, Stream outputPdf, PdfSignOptionsDto request, CancellationToken cancellationToken = default)
     {
-        ArgumentNullException.ThrowIfNull(inputPdf);
-        ArgumentNullException.ThrowIfNull(outputPdf);
         cancellationToken.ThrowIfCancellationRequested();
 
         var (workingInput, ownsWorkingInput) = await EnsureSeekableInputAsync(inputPdf, cancellationToken);
@@ -33,7 +31,7 @@ public sealed class PdfDigitalSignatureService(IOptions<Pkcs11Options> options)
             workingInput.Position = 0;
 
             var pkcs11Options = options.Value;
-            var request = optionsModel ?? new PdfSignOptionsDto();
+
             var uuid = ResolveUuid(request.UUID);
             var reasonWithMeta = BuildReasonWithMeta(request.Reason ?? pkcs11Options.DefaultReason, uuid, sourceHashHex);
 
@@ -47,9 +45,9 @@ public sealed class PdfDigitalSignatureService(IOptions<Pkcs11Options> options)
                 Name = $"Sig_{DateTimeOffset.UtcNow:yyyyMMddHHmmss}"
             };
 
-            var signatureBounds = CreateSignatureBounds(request.VisualSignature);
-            if (signatureBounds is not null)
-                signatureFieldInfo.SignatureBounds = signatureBounds;
+            var left = request.VisualSignature!.Left;
+            var bottom = request.VisualSignature.Bottom;
+            signatureFieldInfo.SignatureBounds = new PdfRectangle(left, bottom, left + request.VisualSignature.Width, bottom + request.VisualSignature.Height);
 
             var builder = new PdfDeferredSignatureBuilder(signerInfo, signatureFieldInfo)
             {
@@ -64,21 +62,18 @@ public sealed class PdfDigitalSignatureService(IOptions<Pkcs11Options> options)
                     ?? PdfCertificationLevel.NoCertification
             };
 
-            if(request.VisualSignature is PdfVisualSignatureOptionsDto visualSignature)
+            builder.SetSignatureAppearance(new PdfSignatureAppearance
             {
-                builder.SetSignatureAppearance(new PdfSignatureAppearance
-                {
-                    AppearanceType = PdfSignatureAppearanceType.Name,
-                    ShowLabels = visualSignature.ShowLabels,
-                    ShowName = true,
-                    ShowDate = false,
-                    ShowReason = false,
-                    ShowLocation = false,
-                    ShowDistinguishedName = false
-                });
-                builder.SetImageData(visualSignature.ImageBytes);
-            }
-
+                AppearanceType = PdfSignatureAppearanceType.Name,
+                ShowLabels = request.VisualSignature.ShowLabels,
+                ShowName = true,
+                ShowDate = false,
+                ShowReason = false,
+                ShowLocation = false,
+                ShowDistinguishedName = false
+            });
+            builder.SetImageData(request.VisualSignature.ImageBytes);
+            
             var deferredSigner = signer.SignDeferred(builder);
             var externalSigner = new Pkcs11ExternalSigner(pkcs11Options);
             deferredSigner.Sign(outputPdf, externalSigner.BuildSignature(deferredSigner.HashValue, digestCalculator.AlgorithmOid));
@@ -92,9 +87,6 @@ public sealed class PdfDigitalSignatureService(IOptions<Pkcs11Options> options)
 
     public async Task SignPdfAsync(Stream inputPdf, Stream outputPdf, IReadOnlyList<PdfSignOptionsDto> optionsList, CancellationToken cancellationToken = default)
     {
-        ArgumentNullException.ThrowIfNull(inputPdf);
-        ArgumentNullException.ThrowIfNull(outputPdf);
-        ArgumentNullException.ThrowIfNull(optionsList);
         cancellationToken.ThrowIfCancellationRequested();
 
         if (optionsList.Count == 0)
@@ -138,7 +130,6 @@ public sealed class PdfDigitalSignatureService(IOptions<Pkcs11Options> options)
 
     public async Task<PdfSignatureCheckResultDto> CheckPdfSignatureAsync(Stream inputPdf, CancellationToken cancellationToken = default)
     {
-        ArgumentNullException.ThrowIfNull(inputPdf);
         cancellationToken.ThrowIfCancellationRequested();
 
         var pdfBytes = await ReadAllBytesAsync(inputPdf, cancellationToken);
@@ -246,8 +237,6 @@ public sealed class PdfDigitalSignatureService(IOptions<Pkcs11Options> options)
 
     public async Task ExtractOriginalPdfAsync(Stream inputPdf, Stream outputPdf, CancellationToken cancellationToken = default)
     {
-        ArgumentNullException.ThrowIfNull(inputPdf);
-        ArgumentNullException.ThrowIfNull(outputPdf);
         cancellationToken.ThrowIfCancellationRequested();
 
         var pdfBytes = await ReadAllBytesAsync(inputPdf, cancellationToken);
@@ -338,18 +327,25 @@ public sealed class PdfDigitalSignatureService(IOptions<Pkcs11Options> options)
             KeyAlgorithm: certificate.PublicKey.Oid?.FriendlyName ?? certificate.PublicKey.Oid?.Value,
             SignatureAlgorithm: certificate.SignatureAlgorithm.FriendlyName ?? certificate.SignatureAlgorithm.Value,
             Pem: ToPem(certificate.RawData),
-            KeySizeBits: TryGetKeySize(certificate));
+            KeySizeBits: TryGetKeySize(certificate, out var keySize) ? keySize : null);
     }
 
-    private static int? TryGetKeySize(X509Certificate2 certificate)
+    private static bool TryGetKeySize(X509Certificate2 certificate, out int keySize)
     {
+        keySize = 0;
         try
         {
-            return certificate.PublicKey.Key.KeySize;
+            using var rsa = certificate.GetRSAPublicKey();
+
+            if (rsa is null)
+                return false;
+
+            keySize = rsa.KeySize;
+            return true;
         }
-        catch
+        catch (CryptographicException)
         {
-            return null;
+            return false;
         }
     }
 
@@ -567,25 +563,6 @@ public sealed class PdfDigitalSignatureService(IOptions<Pkcs11Options> options)
         return pageNumber;
     }
 
-    private static PdfRectangle? CreateSignatureBounds(PdfVisualSignatureOptionsDto? visualOptions)
-    {
-        if (visualOptions is null)
-            return null;
-
-        var left = visualOptions.Left;
-        var bottom = visualOptions.Bottom;
-        var width = visualOptions.Width;
-        var height = visualOptions.Height;
-
-        if (left < 0 || bottom < 0)
-            throw new ArgumentOutOfRangeException(nameof(visualOptions), "VisualSignature.Left and VisualSignature.Bottom cannot be negative.");
-
-        if (width <= 0 || height <= 0)
-            throw new ArgumentOutOfRangeException(nameof(visualOptions), "VisualSignature.Width and VisualSignature.Height must be greater than zero.");
-
-        return new PdfRectangle(left, bottom, left + width, bottom + height);
-    }
-
     private static string BuildReasonWithMeta(string? businessReason, string uuid, string sourceHashHex)
     {
         var trimmedReason = string.IsNullOrWhiteSpace(businessReason) ? null : businessReason.Trim();