diff --git a/src/Controllers/InvoiceController.php b/src/Controllers/InvoiceController.php
index 37dcd64..a58b0b9 100644
--- a/src/Controllers/InvoiceController.php
+++ b/src/Controllers/InvoiceController.php
@@ -271,10 +271,25 @@ class InvoiceController
 
     public function pdf(array $params): void
     {
-        $invoice  = Invoice::find((int)$params['id']);
+        $invoice = Invoice::find((int)$params['id']);
         if (!$invoice) { http_response_code(404); return; }
 
-        // Bei Stornorechnung Originalrechnung laden für Referenzzeile
+        // Gespeicherte PDF aus dem Beleg ausliefern (GoBD: unveränderlicher Stand)
+        if (!empty($invoice['beleg_id'])) {
+            $beleg   = Beleg::find((int)$invoice['beleg_id']);
+            $absPath = $beleg
+                ? dirname(__DIR__, 2) . '/public/' . $beleg['storage_path']
+                : '';
+            if ($absPath && file_exists($absPath)) {
+                header('Content-Type: application/pdf');
+                header('Content-Disposition: attachment; filename="' . $beleg['filename'] . '"');
+                header('Content-Length: ' . filesize($absPath));
+                readfile($absPath);
+                return;
+            }
+        }
+
+        // Fallback: PDF on-the-fly generieren (Entwurf oder Beleg noch ohne Datei)
         if (!empty($invoice['storno_of_id'])) {
             $original = Invoice::find((int)$invoice['storno_of_id']);
             if ($original) {