How to watermark a PDF — in 3 steps
SlimIO's PDF watermark tool stamps semi-transparent text on every page of your document. Everything runs in your browser, so your file stays private and there is nothing to install.
- 1. Add your PDF. Drop in one file, or click to browse.
- 2. Set the watermark. Type your text, then choose diagonal, centered or tiled, a color and the opacity.
- 3. Download. Click Add watermark and save the stamped PDF to your device.
Mark drafts and confidential files
A visible watermark makes it clear a document is a draft, a sample or not for sharing. Pair it with page numbers for review copies, or run the PDF compressor to make the file easier to email.
Watermark PDF — FAQ
How do I add a watermark to a PDF for free?
Open SlimIO's PDF watermark tool, choose a PDF, type your watermark text, pick a style and click Add watermark. The watermarked PDF downloads right away. It runs in your browser, so there is nothing to install and no account needed.
Can I add CONFIDENTIAL or DRAFT to a PDF?
Yes. CONFIDENTIAL is the default text, and you can type DRAFT, SAMPLE, COPY, your company name or anything else.
Will the watermark cover my content?
The watermark is semi-transparent, so the page stays readable. Lower the opacity for a lighter stamp.
Is it safe to watermark a PDF online?
Yes. SlimIO adds the watermark locally in your browser, so your PDF never leaves your device and is not uploaded to a server.
Which characters can I use in the watermark?
The watermark uses a standard Latin font, so letters A–Z, numbers and common punctuation work. Other scripts are not supported yet.