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Watermark a PDF

Type the wording, pick how it sits and how faint it is, and every page gets the same mark drawn into it.

This is a visible mark rather than a lock. It is the right tool for making sure nobody signs the draft by mistake, and the wrong one for stopping somebody who does not want to be stopped.

Questions

Are my files uploaded?
No. Everything happens inside your browser tab. The file is read from your disk, worked on in memory, and saved back to your disk. It is never sent to us or to anyone else, and there is no server here that could receive it. You can confirm it yourself: open your browser's developer tools, look at the Network tab, and run any tool. No request carries your file.
Does a watermark protect my document?
No, and it is worth being clear about that. Anyone with a PDF editor can take it off again. What it does is tell an honest reader what they are holding, which is why DRAFT and COPY are the words most people put there.
How faint should it be?
Faint enough to read the page through, dark enough to notice. Around fifteen percent suits a diagonal mark across text. If you cannot see it in the result, raise it and run the file again.
Will it cover every page?
Yes, every page in the file, including any that are sideways. There is no way to mark only some of them here; run the pages you want through separately and merge them back if you need that.
Can I use my logo instead of text?
Not yet. This draws text only. An image watermark needs the picture embedded and positioned, which is a different tool rather than another setting.
Will it make the file much bigger?
Barely. The text is drawn with one of the standard PDF faces every reader already has, so nothing is embedded and the file grows by a few hundred bytes a page.

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