PDF Watermark Stamper

A leaked draft that looks like the final version, a sample PDF that gets reused without credit, an internal report that ends up forwarded outside the company — a visible watermark is the simplest way to stop a document from being mistaken for something it isn't. This tool stamps a text watermark across every page of a PDF entirely in your browser, without uploading the file anywhere.

Type the watermark text — CONFIDENTIAL, DRAFT, a company name, a case number — and choose how it should sit on the page. Diagonal mode centers one large rotated mark across the page, the classic look for draft and confidential stamps. Tiled mode repeats a smaller version of the same text in a grid across the whole page, which is much harder to crop out of a screenshot or a photocopy than a single central mark. Corner mode places a small, upright watermark in whichever corner you pick, for a subtler credit or attribution line that doesn't interfere with reading the page.

Opacity, font size, rotation angle and color are all adjustable, so the watermark can range from a bold, hard-to-miss stamp to a faint, barely-there mark. Under the hood, the pdf-lib engine embeds a single Helvetica Bold font once and draws the text directly onto each page using the exact width returned by the font metrics, so diagonal and tiled watermarks stay precisely centered regardless of text length or page size — nothing is rasterized, and the underlying page content is left completely untouched.

Because the text is drawn with a built-in Latin (WinAnsi) font rather than a custom-embedded one, accented Latin characters work correctly but non-Latin scripts such as Cyrillic, Arabic or CJK text are not supported and may render as missing or incorrect glyphs — worth knowing before stamping a document in one of those scripts. Everything else runs fully offline: no account, no watermark on the watermarking tool itself, and no size limit beyond what your device's memory allows, which makes it safe to use on contracts, financial statements and other documents you'd rather not upload anywhere.