Update code example to work in evaluation mode

Author: vladimir-litvinchik

Examples/developer-guide/converting-documents/add-watermark-to-converted-document/add_watermark_to_converted_document.py

@@ -16,6 +16,7 @@ def add_watermark_to_converted_document():
 
         # Set up the conversion options
         options = PdfConvertOptions()
+        options.pages_count = 1
         options.watermark = watermark
 
         # Perform the conversion