Add a watermark to a PDF

How to use it

1. Choose a PDF.
2. Type the watermark text and set the colour, size, opacity and whether it sits diagonally or straight.
3. Press Apply and download the watermarked PDF.

A drawn watermark is a label, not a lock

The watermark becomes drawing instructions appended to each page’s content stream - the same kind of instruction as every other mark there. That gives it one genuinely useful property: being part of the page, it survives forwarding, printing, photographing and re-saving in a way a filename or covering note does not. It also means anything able to edit page content can take it out again.

Worth stating plainly, because watermarking is often reached for as though it were protection. It restricts nothing: it does not stop the file being opened, copied or printed, and the text underneath stays selectable through it. What it does is make a document’s status impossible to mistake, so a draft circulated by accident announces itself, and reusing the page elsewhere takes deliberate effort rather than a right-click.

Diagonal placement, and stamping the recipient’s name

Where the mark sits is a deterrence question, not an aesthetic one. A corner stamp is trivially cropped away or covered; text running diagonally across the middle crosses the body of the page, so removing it means removing content. Opacity is the counterweight, and the two are traded against each other - the more a mark resists removal, the more it competes with the words it lies across.

The more useful pattern is changing the text per copy. Stamping each recipient’s name or a reference number produces documents identical except for who they were issued to, so a copy surfacing where it should not identifies its source. That turns a generic deterrent into an accountable one, and is why the text is free-form rather than preset. It still depends on the recipient not bothering to strip it, usually a fair bet: most leaks are forwards, not forgeries.

Questions