[Fixed] missing namespace entry

composer.json

@@ -28,5 +28,10 @@
   "require": {
     "php": "^8.0",
     "oxid-esales/oxideshop-ce": "7.0 - 7.1"
+  },
+  "autoload": {
+    "psr-4": {
+      "D3\\PdfDocuments\\": ""
+    }
   }
 }