squashtools

Add a watermark to a PDF

Draws a watermark over your pages. Your existing content is not altered or re-encoded. See exactly how it will look before you download. Everything happens in your browser, so your file is never uploaded.

Drop your PDF here

or tap to choose a file · stays on your device

How it works

Your browser downloads two small toolkits and runs them locally: pdf.js draws the page previews with a live overlay of your watermark, and pdf-lib draws the real mark into your document.

Adding a watermark draws new text over a page; it never touches or re-encodes anything already there, so your existing text stays selectable and your images keep their original resolution.

The preview overlay is proportional and close, matching position, angle, and text. The final size and font are exactly what pdf-lib renders, so expect the same look within normal tolerance, not a pixel-exact match.

Questions

Does a watermark stop someone copying or editing my PDF?

No. A watermark is not security. It does not prevent copying, editing, or removal by someone determined to do it. It marks the document, nothing more. Treat it as a label, not a lock.

Can the watermark be removed later?

Not from this file. It is drawn straight into each page, the same as any other text on it, not stored as separate removable metadata. To get a version without it, go back to the original file you started with.

Will the watermark make my content unreadable?

It sits over your content, so opacity matters. Light is subtle enough to read straight through in most cases; Strong is more visible but more assertive. Pick the level that fits how you plan to use the file.

What happens on sideways or rotated pages?

The watermark lands and tilts the way the reader sees the page, not the raw unrotated page underneath it. The same rotation handling that page-numbers uses. Rotate PDF.

What is out of scope in this version?

Logo or image watermarks (may come later), placing the mark behind your content instead of over it, tiling or repeating it across a page, and a custom angle beyond diagonal or horizontal. All deliberate limits for now, not oversights.

I want to number pages, not watermark them.

That is a separate tool. Page Numbers.

Are my files uploaded to a server?

No. Both the page previews and the actual watermarking happen inside your browser, using pdf.js for the thumbnails and pdf-lib for the output, which your browser downloads once and runs locally. Your file never leaves your device.

What does "Compress this PDF first" do on the result?

It sends your watermarked PDF straight to the compress tool without you having to download it and pick it again. The file is held briefly in your browser’s own storage, never sent anywhere, and is deleted the moment the compress tool loads it.

Does this work offline?

Yes. Tap Use offline, or just use the tool once, and it keeps working with no connection at all. Your files never travel anywhere. With your internet switched off, you can watch that be true.