Add a watermark to a PDF

Add a diagonal text watermark to contracts, drafts, tender responses, or review copies without sending the PDF to a server. Enter wording such as CONFIDENTIAL, DRAFT, or the name of the person receiving the file, choose a size and an opacity, then apply it to every page or to ranges such as 1-3, 8. Leaving the range field empty marks the whole document.

A watermark states intent; it does not enforce anything. The text is drawn on top of existing page content, so anyone can still read, copy, print, and forward the file, and a determined recipient with a PDF editor can take the mark off again. If the requirement is that the document cannot be opened at all without a password, that is the protect tool, not this one. What a watermark does well is make a leaked copy embarrassing and traceable, which is why marking each review copy with its recipient’s name is more useful than marking them all as CONFIDENTIAL.

Pages are not rasterised. The mark is added as page content in a standard font, so the underlying text stays selectable and searchable and the file does not swell. One consequence is worth knowing: because the watermark is real text, it is selectable too, and anyone copying a page will pick up the word DRAFT along with the paragraph they wanted.

The standard font covers Latin script and the accented characters that go with it, so CONFIDENTIEL and Vertraulich are fine. Text in Chinese, Japanese, Devanagari, Arabic, or Cyrillic cannot be encoded and is refused with a message naming the character, rather than being silently dropped from the output.

Keep opacity light over dense pages. A strong mark across a table of figures makes the numbers harder to read for the reviewer you sent it to, which defeats the purpose of circulating a draft at all.

Everything happens in a browser worker on your machine. Documents that need marking as confidential are exactly the ones that should not be uploaded to a queue to have the word added. Password-protected files have to be unlocked first.