diff --git a/EnvelopeGenerator.Server/EnvelopeGenerator.Server.Client/Pages/SenderEditorPage.razor b/EnvelopeGenerator.Server/EnvelopeGenerator.Server.Client/Pages/SenderEditorPage.razor
index 59f2e6fd..8900b5a6 100644
--- a/EnvelopeGenerator.Server/EnvelopeGenerator.Server.Client/Pages/SenderEditorPage.razor
+++ b/EnvelopeGenerator.Server/EnvelopeGenerator.Server.Client/Pages/SenderEditorPage.razor
@@ -159,18 +159,29 @@
                 </button>
 
                 @* PDF Upload *@
-                <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;">
-                    <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>
-                    @L("UploadPdf", "PDF hochladen")
-                    <InputFile OnChange="OnPdfFileSelectedAsync"
-                               accept=".pdf"
-                               style="display: none;" />
-                </label>
+                @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;">
+                        <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>
+                        @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>
+                }
 
                 @if (_pdfLoaded && _signatureFields.Count > 0)
                 {
@@ -256,14 +267,24 @@
                     <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>
-                    <label class="btn btn-light btn-sm" style="cursor: pointer; font-weight: 500;">
-                        <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>
-                        @L("UploadPdf", "PDF hochladen")
-                        <InputFile OnChange="OnPdfFileSelectedAsync" accept=".pdf" style="display: none;" />
-                    </label>
+                    @if (_isPageReady)
+                    {
+                        <label class="btn btn-light btn-sm" style="cursor: pointer; font-weight: 500;">
+                            <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>
+                            @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>
+                    }
                 </div>
             </div>
         }
@@ -468,6 +489,7 @@
 
     // ── State ──
     bool _pdfLoaded = false;
+    bool _isPageReady;
     string _fileName = string.Empty;
     string? _errorMessage;
     byte[]? _originalPdfBytes;  // Pristine upload — never modified, used as base for redraw
@@ -534,6 +556,17 @@
             return;
     }
 
+    protected override Task OnAfterRenderAsync(bool firstRender)
+    {
+        if (firstRender)
+        {
+            _isPageReady = true;
+            StateHasChanged();
+        }
+
+        return Task.CompletedTask;
+    }
+
     async Task LoadEnvelopeForEditAsync(int envelopeId)
     {
         if (_isLoadingEnvelopeForEdit)
@@ -622,6 +655,9 @@
     // ── PDF upload ──
     async Task OnPdfFileSelectedAsync(InputFileChangeEventArgs e)
     {
+        if (!_isPageReady)
+            return;
+
         _errorMessage = null;
         var file = e.File;
         if (file is null) return;
diff --git a/EnvelopeGenerator.sln b/EnvelopeGenerator.sln
index a8be861b..a8a36ad6 100644
--- a/EnvelopeGenerator.sln
+++ b/EnvelopeGenerator.sln
@@ -41,6 +41,7 @@ EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "EnvelopeGenerator.Server", "EnvelopeGenerator.Server", "{BF1700D5-592E-4FFA-84E8-5480E289A1F0}"
 	ProjectSection(SolutionItems) = preProject
 		EnvelopeGenerator.Server\publish.bat = EnvelopeGenerator.Server\publish.bat
+		SENDER_SAVE_EDIT_MIGRATION_PLAN.md = SENDER_SAVE_EDIT_MIGRATION_PLAN.md
 	EndProjectSection
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "EnvelopeGenerator.Server", "EnvelopeGenerator.Server\EnvelopeGenerator.Server\EnvelopeGenerator.Server.csproj", "{4E6C54DA-576D-0955-2564-9EC890BB8279}"