Add a watermark to a PDF
Mark a document as CONFIDENTIAL, DRAFT or with your name before sharing it. The watermark is drawn diagonally across every page.
Runs on your device · 0 bytes uploaded
How to watermark PDF
- Add one PDF file.
- Type the watermark text and choose how see-through it is.
- Click “Add watermark” and download.
Private by design — and you can check
Your files are never uploaded, because there is nowhere to upload them to.
- No upload step existsFiles are read and written inside this browser tab. There is no server that could receive them.
- The browser enforces itThis page’s Content Security Policy only allows connections back to this site, which serves nothing but the app itself.
- See for yourselfOpen developer tools, watch the Network tab and run a job: no request carries your document.
- Open sourceEvery line is on GitHub, built on qpdf, pdf.js and pdf-lib.
Frequently asked questions
Are my files uploaded anywhere?
No. ZapDoc does the work inside your browser tab, using open-source engines compiled to WebAssembly and JavaScript. Your file is read from your device, processed locally, and the result is saved straight back to your device. You can check this yourself: open your browser’s developer tools, go to the Network tab, and run a job — no request carries your file.
Can the watermark be removed?
A text watermark discourages copying but a determined person with a PDF editor can remove it. For stronger protection, also use Protect PDF.
Which characters can I use?
Letters, numbers and common symbols in Latin script. Other scripts are not supported by the standard PDF fonts.
Is ZapDoc free?
Yes. There is no sign-up, no watermark and no daily limit. ZapDoc is open source under the MIT license.
More private tools
- Merge PDFCombine several PDFs into one, in the order you choose.
- Split PDFExtract the pages you need into a new PDF.
- Rotate PDFTurn sideways pages the right way, permanently.
- Delete PDF PagesRemove pages you don’t want to share.
- Unlock PDFSave a copy without the password you know.
- Protect PDFLock a PDF with a password and AES-256 encryption.
- Remove PDF MetadataStrip author, title, software and XMP details.
- JPG to PDFTurn photos and scans into one PDF.