How to watermark
- Add one or more PDFs.
- Type the text. Short words work best diagonally: CONFIDENTIAL, DRAFT, COPY, SAMPLE.
- Choose Centre, diagonal for a classic watermark, or a corner for a small label.
- Set the size, angle, opacity and colour.
- Click Add watermark and download.
Uses
- DRAFT on documents circulated for comment, so nobody mistakes them for the final version.
- CONFIDENTIAL or COMMERCIAL IN CONFIDENCE on tenders, board papers and pricing.
- Copy for [recipient] on identity documents you send, a practice often recommended to limit misuse: if a copy of your passport marked "Copy for XYZ rental application, October 2026" leaks, it is harder to reuse elsewhere and its source is obvious.
- SAMPLE on previews of paid documents.
Watermarking ID copies
When a real-estate agent, employer or service asks for a copy of your licence or passport, consider watermarking it with who it is for, the purpose and the date. Keep the text over the document but clear of the photo and the key numbers, so it is still accepted. A semi-transparent diagonal watermark at 20–30% opacity across the middle is usually readable and hard to crop out. Check first whether the recipient accepts watermarked copies; some identity verification processes do not.
Settings that look right
- Diagonal: size 60–90 pt, angle 45°, opacity 15–25%, a mid grey or red.
- Corner label: size 9–12 pt, opacity 100%, dark grey.
- Long text (a sentence) works better in a corner or along the bottom than diagonally.
The diagonal watermark is centred on each page using that page's own size, so mixed page sizes are handled.
How strong is a watermark?
The text is drawn into each page's content, so it appears in every viewer, prints, and cannot be switched off as a layer. It is still text in the PDF, so it can be searched, and someone with editing software and some effort could remove it. For stronger protection combine it with a password to limit who can open the file, or with strong compression, which turns pages into images with the watermark burnt in and makes removal much harder.
Fonts and characters
Watermarks use Helvetica Bold, a standard PDF font that every viewer can display without embedding. It covers the Latin alphabet, including accented letters; characters outside it, such as Chinese, Arabic or emoji, cannot be drawn with standard fonts and are replaced.
Watermarking several files
Add several PDFs and every one gets the same watermark, which suits a batch of drafts or a set of ID copies for the same purpose. The watermark is centred on each page using that page's own size, so A4, Letter and landscape pages all look right.
Readability
A watermark should be obvious without making the document hard to read. Diagonal text at 15–25% opacity in mid grey sits behind the content visually even though it is drawn on top. Red reads as a warning (DRAFT, NOT FOR CIRCULATION); grey reads as a label (COPY). Test on a page with dense text before running a long document, and check the printed result if the document will be printed; light watermarks can vanish on some printers.
Watermarks and accessibility
Screen readers may read the watermark text along with the page. For accessible documents keep watermarks short, and avoid putting essential information only in a watermark.
Watermarks versus stamps
A watermark marks every page, usually large and faint. A stamp, such as RECEIVED with a date or an approval mark, is small and placed once. For a one-off stamp, use the Sign PDF text tool to place text exactly where you want it on a single page.
Removing a watermark you added
Watermarks are drawn into the pages, so they cannot be switched off later. Keep your un-watermarked original, and watermark a fresh copy each time you share it with someone new.
Colour choice
The colour picker sets the watermark colour; mid grey (for COPY or SAMPLE) and a muted red (for DRAFT or CONFIDENTIAL) are conventional. Very light colours at low opacity may disappear when printed or photocopied, which defeats the purpose of marking a printed copy.
Run a single test page first if you are unsure of the settings; it takes seconds.
Keep the original, un-watermarked file somewhere safe, so you can make a fresh copy for each new recipient.
Privacy: the file stays on your device
Online PDF services upload your document to their servers, process it there and keep it for a while. This tool does the work in your browser. The file is read into the page's memory, processed by open-source libraries (pdf-lib for editing and pdf.js for rendering) in a background worker, and the result is offered back as a download. Nothing is sent anywhere, there is no account, and closing the tab discards everything. You can check it: open your browser's developer tools, watch the Network tab while you run the tool, and you will see no upload. After the page has loaded once it also works offline.