Add a watermark to PDF

Your files and your privacy

The PDF and any logo image you add are never uploaded. Both are read into this browser tab, stamped by a Web Worker on your own device, and returned as a download. The page’s Content-Security-Policy restricts connect-src to this origin, so an upload would be blocked by the browser even if the code attempted one.

What this tool does

Mark a PDF as a draft, as confidential, or as yours, without uploading it. Text is drawn across the pages at the size, angle, opacity and position you choose, on every page or only the ones you name. A companion operation stamps a PNG or JPEG instead when you need a logo or a signature.

A watermark is drawn on top of the existing page content at the position, size, angle and opacity you choose. Text watermarks use a font built into the PDF format, so no font file is embedded and the file barely grows. Tiling repeats the mark in a grid across the whole page, which is much harder to crop away than a single centred stamp. A separate Image watermark operation in the same toolkit places a PNG or JPEG instead — a company logo, a scanned signature, or a phrase in a script the built-in fonts cannot draw.

How to use it

1. Select Choose a PDF file, then type the text to stamp, such as DRAFT or the recipient’s name.
2. Pick a position: the centre, one of the four corners, or tiled across the page.
3. Set the font size, the angle, and the opacity. Around 25% keeps the mark visible without burying the text underneath.
4. Leave the pages box empty to mark every page, or name pages such as “1” for a cover sheet or “2-” for everything after it.
5. Select Run, then Download. To stamp a logo instead, switch to the Image watermark operation and choose a PNG or JPEG.

Example use cases

• Marking a contract DRAFT so a reviewer cannot mistake it for the version to sign.
• Stamping each recipient’s name across a circulated report so a leaked copy can be traced.
• Putting SPECIMEN across a sample invoice or certificate before publishing it as an example.
• Adding a company logo to the corner of every page of a proposal before sending it out.

Supported input and output

Accepts

• PDF (application/pdf), one file, up to 50 MB
• Latin text for the text watermark; PNG or JPEG up to 30 MB for the image watermark
• Unencrypted documents only

Produces

• A PDF named <original>-watermarked.pdf

What this tool will not do

• A watermark is a visible mark, not a security control. Anyone who can open the file can still read, copy and print it, the mark can be cropped or removed with an editor, and the text underneath stays selectable through it.
• Text watermarks can only draw characters the fonts built into the PDF format support, which is Latin. Chinese, Japanese, Korean, Arabic, Hebrew and most emoji are refused with an explanation; render them as a PNG and use the image watermark.
• The text is not scaled to fit. A long phrase at a large font size is positioned by its measured width and simply runs past the page edges, where it is clipped.
• Positions are worked out from the unrotated size of the mark, and pdf-lib turns it about its anchor point, so an angled stamp sits a little off the spot a 0° stamp would occupy.
• The text colour is fixed at a mid grey in this panel; only size, angle, opacity and position are adjustable.
• Tiling stops after 400 stamps on a page, which is a guard against a tiny font on a large page rather than a setting.
• It will not open a password-protected PDF, and it cannot add a password either.
• Any digital signature on the input is invalidated, because the saved file is a new document.

Common mistakes

• Treating the watermark as protection. It does not restrict opening, copying or printing, and a document that must not be read by someone needs access control instead.
• Setting the opacity so low that it disappears when the page is printed in greyscale, or so high that it hides the figures underneath. Check the result at the size it will actually be read.
• Using a single centred stamp on a document that might be cropped or re-photographed. One mark is trivial to cut off; tiling is not.
• Typing a long line at the default 48 points and only noticing later that both ends are missing. Shorten the text or reduce the size until it fits the narrowest page.
• Forgetting that the watermark text is real text in the output. It is selectable and searchable like any other text on the page.

Technical notes

Both watermark operations run through pdf-lib inside a Web Worker. Text is drawn with the standard Helvetica-Bold face, which is WinAnsi-encoded; the text is test-encoded before any page is touched so unsupported characters produce a clear message instead of a failure halfway through writing the file. Positions are computed in PDF user space with its bottom-left origin, and tiling builds a grid that starts off-page so the pattern reaches the edges, with generous spacing so the marks stay readable. The image watermark embeds a PNG or JPEG once and re-draws that single embedded object at every spot, sizing it as a fraction of each page’s width so mixed page sizes stay consistent.

Frequently asked questions

Can a watermark stop someone copying my document?

No. It is a visible mark and nothing more. It discourages casual reuse and makes a leaked copy traceable, but anyone who can open the file can read, copy and print it, and an editor can remove the mark.

Why was my watermark text rejected?

The fonts built into the PDF format cover Latin characters only, so text in Chinese, Japanese, Korean, Arabic, Hebrew or emoji cannot be drawn with them. Render the phrase as a PNG and use the Image watermark operation instead.

Can I use a logo instead of text?

Yes. The Image watermark operation in the same toolkit stamps a PNG or JPEG, with its width set as a percentage of the page width, plus the same opacity, angle and position controls. A PNG with a transparent background gives the cleanest result.

Can I watermark only some pages?

Yes. The pages box takes the same syntax as the other tools, for example “1” for a cover page or “3-8” for a span. Leave it empty to mark every page in the document.

Will the watermark make the file much bigger?

A text watermark adds almost nothing, because the font is built into the PDF format and is not embedded. An image watermark embeds the picture once and reuses it on every page, so the increase is roughly the size of that one image.

Can I remove a watermark from a PDF here?

No. This toolkit adds marks; it does not take them off. Once drawn, the watermark is part of the page content in the file you downloaded, so keep the unmarked original.