Watermark PDF

The Watermark PDF tool overlays semi-transparent diagonal text across every page of a document, the quick way to mark a file as DRAFT, CONFIDENTIAL, a copy holder’s name, or a sample.

Drop in a PDF, type the watermark text, and tune three things: the font size, the rotation angle, and the opacity.

The watermark is centered and rotated on each page regardless of page size, and the text is measured before placement so it stays balanced whether the page is A4 portrait or a wide landscape slide.

Lower opacity keeps the underlying content readable while still making the status unmistakable; a steeper angle and larger size push the message toward an unmissable stamp.

Because the watermark is drawn as a real text layer rather than a flattened image, file sizes barely change and the original text underneath stays selectable.

Every page in the document receives the same mark in one pass.

It all runs locally with pdf-lib inside your browser, so sensitive drafts and contracts never get uploaded, and the tool keeps working offline once the page has loaded.

The source file is read only — you download a new watermarked copy and your original stays exactly as it was.

Note that a text watermark is a visual deterrent, not encryption: it discourages casual reuse but does not lock the file.