Use a watermark as a visible label
Add text such as Draft or Confidential, or choose an image watermark. Position it in the preview and adjust size, angle, and opacity so the document remains readable.
A watermark can communicate handling instructions or ownership, but it is not encryption, access control, or a legal proof of authorship. Do not rely on a visible stamp to protect confidential data.
Inspect every page
The same placement can cover different content on pages with different layouts. Review the saved PDF, especially tables, signatures, and small print. Try lighter opacity or a different position if the overlay obscures information.
The document is processed locally and the original is not overwritten. Save a separate copy so you can change the watermark later.