Sending a document for review without marking it as a draft is how a preliminary version ends up signed, forwarded to a client, or quoted back at you six months later. A watermark across every page is cheap insurance.
Adding one
The stamp is drawn diagonally across the centre of every page. The file is processed in your browser and never uploaded.
Choosing the opacity
This is the setting that decides whether the watermark works.
Too light and people miss it, which defeats the purpose. Too heavy and reviewers struggle with the content, which also defeats the purpose. Start at 30% and look at the result on a page with dense text before committing.
Colour matters too: mid-grey reads as deliberate, red reads as urgent, and both work. Very light yellow or pale blue often disappears entirely once printed in black and white.
What a watermark actually protects against
Being straight about this, because a lot of tools are not.
It does protect against confusion. Someone opening a document marked DRAFT knows not to countersign it. Someone forwarding a page marked CONFIDENTIAL — YOUR NAME knows it is traceable. This is real and it is the main reason to use one.
It does not protect against a determined person. The watermark is drawn into the page content, not encrypted. Anyone with a proper PDF editor can select and delete it, and there is no way to make that harder in a PDF that also has to be readable.
So: a watermark is a signal and a deterrent, not a lock. If your document genuinely must not be redistributed, the answer is access control — send it through a system that tracks who opened it — not a graphic on the page.
Personalised watermarks for tracking
A technique worth knowing: when circulating a confidential document to several people, watermark each copy with the recipient's name.
If a copy later appears somewhere it should not, the watermark identifies which recipient it came from. That knowledge alone changes behaviour — people are more careful with a document that has their name across it.
It means producing one file per recipient, which is a few minutes for a distribution list of ten. For sensitive material it is usually worth it.
What to watch after applying
Check a dense page. Somewhere with a full page of text or a detailed table. If the watermark makes those hard to read, reduce the opacity.
Check any page with a signature block. A DRAFT stamp across a signature line is exactly right for a draft, and exactly wrong if you later reuse the file as the final version.
Keep the un-watermarked original. The watermark becomes page content and cannot be removed cleanly afterwards. When the draft becomes final, you want to generate the final from the clean source, not try to strip the stamp.
Watermark last
If your workflow also involves merging, splitting or compressing, watermark at the end. Watermarking first and then merging means the stamp may be inconsistent across sections, and re-compressing a watermarked file can make the stamp blotchy where it overlaps images.