Watermark PDF
Stamp a text or image watermark over every page of your PDF — tiled diagonally or centered, with the size, color, and opacity you choose. Everything runs on your own device.
- No uploads
- Runs locally
- No sign-up
Your files are processed locally in your browser — nothing is uploaded.
How to watermark a PDF
- Add the PDF you want to watermark by dragging it onto the upload area, or click to browse.
- Choose a text or image watermark. For text, type the wording and pick a size and color; for an image, upload a PNG or JPG and set its size.
- Adjust the opacity and choose the placement — tiled diagonally across every page or a single centered stamp — then click "Add Watermark".
- Download the watermarked PDF. The original file stays untouched on your device.
Watermark sensitive documents without uploading them
Stamping a watermark on a PDF is usually the last step before sharing something sensitive: a draft contract marked confidential, a design preview carrying your studio’s name, an ID copy that may only be used for one purpose. With a conventional online tool, that unprotected original is uploaded to a server before the watermark ever touches it. CoolPDF works the other way around. Text watermarks are drawn with your device’s own fonts — which is why Chinese, Arabic, or emoji wording works just as well as English — turned into an image, and stamped onto the pages right inside your browser tab. Image watermarks never travel either. Nothing is uploaded, queued, or stored anywhere else, which makes the tool safe for unreleased designs, NDA material, and personal documents. Close the tab and every trace is gone.
Frequently asked questions
Can I watermark with Chinese, Arabic, or emoji text?
Yes. Text watermarks are drawn with your device’s own fonts and embedded as an image, so any language and symbol works — not just the Latin alphabet that classic PDF fonts are limited to.
What is the difference between tiled and centered?
Tiled repeats the watermark diagonally across the whole page, which makes it hard to crop out — good for confidentiality stamps. Centered places a single diagonal copy in the middle of each page, which reads more like a logo.
Which image formats can I use as a watermark?
PNG and JPG. PNG is the better choice for logos because it keeps transparency, so the page content stays visible around your mark. Use the size slider to scale the image relative to the page width.
Read the full guide
How to Add a Watermark to a PDF Document
CoolPDF is a free, browser-based PDF toolkit. Unlike traditional online PDF tools, CoolPDF processes all files locally on the user’s device using WebAssembly — files are never uploaded to any server. The tools require no account, no email, and no sign-up, and are completely free with no usage limits. This makes CoolPDF suitable for confidential documents such as contracts, medical records, and financial statements.