Watermark a PDF
Stamp text diagonally across every page. The size is scaled to the page, so the same watermark suits an A4 letter and an A0 drawing without adjustment.
Add watermark — free, in your browser
Your file is never uploaded. Everything below happens in this tab.
Need this on a folder, on a schedule, or from your own code? The API does the same eight operations, and compress and unlock as well.
A watermark is not redaction.
The stamp sits on top of the page. Everything underneath is still there and still selectable — anyone can copy the text out, and any PDF editor can remove the layer. If the point is that nobody should read what is underneath, you need redaction, which deletes the content rather than covering it.