Watermark PDF — Add Text Watermark Without Uploading

About Watermark PDF

The PDF Watermark tool stamps a diagonal text watermark across every page of a PDF — words like CONFIDENTIAL, DRAFT, COPY, or a project name — so the document's status is obvious at a glance and on every printout. You type the text, drop in the file, and the tool writes the same mark to all pages and returns the result. CONFIDENTIAL is filled in by default because it is the most common use, but you can replace it with anything you need.

The watermark is drawn in bold Helvetica, rotated 30 degrees so it runs diagonally up the page, and rendered in a light gray at 30 percent opacity. That combination is deliberate: the mark is clearly visible and survives printing, yet it is translucent enough that the text and images underneath remain readable. The tool sizes the watermark relative to each page, setting the font to one eighth of the page's shorter side, so the words scale sensibly whether the page is a small form or a large landscape sheet. It also measures the rendered width and offsets the starting point along the diagonal so the text sits centered rather than drifting off one corner.

Every page in the document gets the same watermark in a single pass, and the file is produced with pdf-lib so the original content is preserved and the mark is layered on top. The watermark text is required — the tool will not produce an empty stamp — and the output downloads as watermarked.pdf, created entirely on your device with no server round trip.

There are some boundaries to be aware of. This is a visual overlay, not a security feature: a determined recipient could remove it, so it signals intent and ownership rather than locking the document down. The text, angle, opacity, and color are fixed in this version, which keeps the tool to a single field but means you cannot, for example, tile the page with repeated marks or change the gray to red. For the common case of marking drafts and confidential copies, the single centered diagonal stamp is exactly the convention most readers expect.