What is the difference between a watermark and a stamp?

In the PDF format, a stamp is usually an annotation: a label that sits on top of the page and that PDF editors can select, move, or delete. This tool draws the text into each page's own content instead, at 45 degrees and the opacity you choose, so it prints with the page like a classic watermark.

Can I stamp a different label on each page?

Currently the same watermark text is applied to every page. If you need page-specific labels, process the PDF in separate runs.

What font is used for the watermark?

The watermark uses Helvetica Bold, which is a standard PDF font available in all PDF viewers without embedding.

Is there a page limit?

Any number of pages, as long as the file is 100 MB or smaller. The tool renders a thumbnail of every page when the PDF loads, so a document with hundreds of pages takes longer, and a phone can run short of memory well before 100 MB.

Where is my PDF processed?

All processing runs in your browser. As a second layer, the site's Content Security Policy tells your browser to block the kinds of requests a script would use to upload a file.

Stamp PDF Pages

Stamp a diagonal text label across every page of your PDF, ideal for marking documents as DRAFT, CONFIDENTIAL, or SAMPLE before sharing. All settings are adjustable and everything runs in your browser.

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How it works

pdf-lib loads your PDF in memory and draws the label into each page's content in Helvetica Bold, rotated 45 degrees around the centre of the visible page area, at the opacity and colour you chose. Landscape and rotated pages are handled as they are displayed, and a label too long for a page is scaled down on that page. The document properties are kept, and the result downloads as a new file.

Processing runs in your browser

All processing happens inside your browser tab. pdf-lib applies the watermark entirely in memory; our servers are not involved at any point.

Related operations

For tagging each page with a numeric label, try PDF page numbers. To bundle watermarked files into one PDF, use merge PDF. For shrinking the marked output, see compress PDF.

Frequently asked questions

What is the difference between a watermark and a stamp?: In the PDF format, a stamp is usually an annotation: a label that sits on top of the page and that PDF editors can select, move, or delete. This tool draws the text into each page's own content instead, at 45 degrees and the opacity you choose, so it prints with the page like a classic watermark.
Can I stamp a different label on each page?: Currently the same watermark text is applied to every page. If you need page-specific labels, process the PDF in separate runs.
What font is used for the watermark?: The watermark uses Helvetica Bold, which is a standard PDF font available in all PDF viewers without embedding.
Is there a page limit?: Any number of pages, as long as the file is 100 MB or smaller. The tool renders a thumbnail of every page when the PDF loads, so a document with hundreds of pages takes longer, and a phone can run short of memory well before 100 MB.
Where is my PDF processed?: All processing runs in your browser. As a second layer, the site's Content Security Policy tells your browser to block the kinds of requests a script would use to upload a file.

Last reviewed September 30, 2026

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