diff --git a/EnvelopeGenerator.Server/EnvelopeGenerator.Server.Client/Pages/SenderEditorPage.razor b/EnvelopeGenerator.Server/EnvelopeGenerator.Server.Client/Pages/SenderEditorPage.razor
index 8900b5a6..70dc8a0e 100644
--- a/EnvelopeGenerator.Server/EnvelopeGenerator.Server.Client/Pages/SenderEditorPage.razor
+++ b/EnvelopeGenerator.Server/EnvelopeGenerator.Server.Client/Pages/SenderEditorPage.razor
@@ -159,29 +159,43 @@
                 </button>
 
                 @* PDF Upload *@
-                @if (_isPageReady)
-                {
-                    <label class="pdf-toolbar__btn"
-                           title='@L("UploadPdf", "PDF hochladen")'
-                           style="cursor: pointer; display: inline-flex; align-items: center; gap: 0.3rem; padding: 0.3rem 0.75rem; font-size: 0.75rem; font-weight: 500;">
+                <label class="pdf-toolbar__btn"
+                       title='@L("UploadPdf", "PDF hochladen")'
+                       style="cursor: @((_isPageReady && !_isPdfUploadInProgress) ? "pointer" : "not-allowed");
+                              opacity:@((_isPageReady && !_isPdfUploadInProgress) ? "1" : "0.6");
+                              display: inline-flex; align-items: center; gap: 0.3rem; padding: 0.3rem 0.75rem; font-size: 0.75rem; font-weight: 500;">
+                    @if (_isPdfUploadInProgress)
+                    {
+                        <span class="spinner-border spinner-border-sm" role="status" style="width:0.8rem;height:0.8rem;border-width:2px;"></span>
+                    }
+                    else
+                    {
                         <svg xmlns="http://www.w3.org/2000/svg" width="14" height="14" fill="currentColor" viewBox="0 0 16 16">
                             <path d="M.5 9.9a.5.5 0 0 1 .5.5v2.5a1 1 0 0 0 1 1h12a1 1 0 0 0 1-1v-2.5a.5.5 0 0 1 1 0v2.5a2 2 0 0 1-2 2H2a2 2 0 0 1-2-2v-2.5a.5.5 0 0 1 .5-.5z" />
                             <path d="M7.646 1.146a.5.5 0 0 1 .708 0l3 3a.5.5 0 0 1-.708.708L8.5 2.707V11.5a.5.5 0 0 1-1 0V2.707L5.354 4.854a.5.5 0 1 1-.708-.708l3-3z" />
                         </svg>
+                    }
+                    @if (_isPdfUploadInProgress)
+                    {
                         @L("UploadPdf", "PDF hochladen")
-                        <InputFile OnChange="OnPdfFileSelectedAsync"
-                                   accept=".pdf"
-                                   style="display: none;" />
-                    </label>
-                }
-                else
-                {
-                    <span class="pdf-toolbar__btn"
-                          style="opacity:0.6; cursor:not-allowed; display: inline-flex; align-items: center; gap: 0.3rem; padding: 0.3rem 0.75rem; font-size: 0.75rem; font-weight: 500;">
-                        <span class="spinner-border spinner-border-sm" role="status" style="width:0.8rem;height:0.8rem;border-width:2px;"></span>
-                        @L("Loading", "Wird geladen")…
-                    </span>
-                }
+                        @:
+                        @:...
+                    }
+                    else if (_isPageReady)
+                    {
+                        @L("UploadPdf", "PDF hochladen")
+                    }
+                    else
+                    {
+                        @L("Loading", "Wird geladen")
+                        @:
+                        @:...
+                    }
+                    <InputFile OnChange="OnPdfFileSelectedAsync"
+                               accept=".pdf"
+                               disabled="@(!_isPageReady || _isPdfUploadInProgress)"
+                               style="display: none;" />
+                </label>
 
                 @if (_pdfLoaded && _signatureFields.Count > 0)
                 {
@@ -267,24 +281,42 @@
                     <p class="text-white mb-4" style="opacity: 0.75; font-size: 0.85rem;">
                         @L("SenderEditor_UploadPdfToPlaceFields", "Laden Sie eine PDF-Datei hoch, um Signaturfelder zu platzieren.")
                     </p>
-                    @if (_isPageReady)
-                    {
-                        <label class="btn btn-light btn-sm" style="cursor: pointer; font-weight: 500;">
+                    <label class="btn btn-light btn-sm"
+                           style="cursor: @((_isPageReady && !_isPdfUploadInProgress) ? "pointer" : "not-allowed");
+                                  opacity:@((_isPageReady && !_isPdfUploadInProgress) ? "1" : "0.8");
+                                  font-weight: 500;">
+                        @if (_isPdfUploadInProgress)
+                        {
+                            <span class="spinner-border spinner-border-sm me-1" role="status" style="width:0.8rem;height:0.8rem;border-width:2px;"></span>
+                        }
+                        else
+                        {
                             <svg xmlns="http://www.w3.org/2000/svg" width="14" height="14" fill="currentColor" class="me-1" viewBox="0 0 16 16">
                                 <path d="M.5 9.9a.5.5 0 0 1 .5.5v2.5a1 1 0 0 0 1 1h12a1 1 0 0 0 1-1v-2.5a.5.5 0 0 1 1 0v2.5a2 2 0 0 1-2 2H2a2 2 0 0 1-2-2v-2.5a.5.5 0 0 1 .5-.5z" />
                                 <path d="M7.646 1.146a.5.5 0 0 1 .708 0l3 3a.5.5 0 0 1-.708.708L8.5 2.707V11.5a.5.5 0 0 1-1 0V2.707L5.354 4.854a.5.5 0 1 1-.708-.708l3-3z" />
                             </svg>
+                        }
+                        @if (_isPdfUploadInProgress)
+                        {
                             @L("UploadPdf", "PDF hochladen")
-                            <InputFile OnChange="OnPdfFileSelectedAsync" accept=".pdf" style="display: none;" />
-                        </label>
-                    }
-                    else
-                    {
-                        <button class="btn btn-light btn-sm" type="button" disabled>
-                            <span class="spinner-border spinner-border-sm me-1" role="status" style="width:0.8rem;height:0.8rem;border-width:2px;"></span>
-                            @L("Loading", "Wird geladen")…
-                        </button>
-                    }
+                            @:
+                            @:...
+                        }
+                        else if (_isPageReady)
+                        {
+                            @L("UploadPdf", "PDF hochladen")
+                        }
+                        else
+                        {
+                            @L("Loading", "Wird geladen")
+                            @:
+                            @:...
+                        }
+                        <InputFile OnChange="OnPdfFileSelectedAsync"
+                                   accept=".pdf"
+                                   disabled="@(!_isPageReady || _isPdfUploadInProgress)"
+                                   style="display: none;" />
+                    </label>
                 </div>
             </div>
         }
@@ -490,6 +522,7 @@
     // ── State ──
     bool _pdfLoaded = false;
     bool _isPageReady;
+    bool _isPdfUploadInProgress;
     string _fileName = string.Empty;
     string? _errorMessage;
     byte[]? _originalPdfBytes;  // Pristine upload — never modified, used as base for redraw
@@ -658,6 +691,9 @@
         if (!_isPageReady)
             return;
 
+        if (_isPdfUploadInProgress)
+            return;
+
         _errorMessage = null;
         var file = e.File;
         if (file is null) return;
@@ -670,6 +706,9 @@
 
         try
         {
+            _isPdfUploadInProgress = true;
+            await InvokeAsync(StateHasChanged);
+
             const long maxBytes = 50 * 1024 * 1024;
             using var ms = new System.IO.MemoryStream();
             await file.OpenReadStream(maxBytes).CopyToAsync(ms);
@@ -695,6 +734,11 @@
                 ex.Message);
             Logger.LogError(ex, "Failed to load PDF file");
         }
+        finally
+        {
+            _isPdfUploadInProgress = false;
+            await InvokeAsync(StateHasChanged);
+        }
     }
 
     // ── Placement mode ──