PDF watermark

How to use it

1. Drop one PDF on the card, paste with ⌘V / Ctrl+V, or press “Choose PDF”. A watermark is applied immediately with the default settings — the text “CONFIDENTIAL”, centred, 45°, 25% opacity, 48 pt, gray. There is no Apply button.
2. Edit the watermark text. Choose “Centre” or “Tile”, then open “More options” to change the angle, opacity, font size or colour. The paper preview updates instantly and the PDF rebuilds a moment later. Chinese, Arabic and emoji are drawn with your system fonts.
3. The status turns green and says “Watermark ready · N pages” when the new PDF is built. Download it, or open “Preview” to check the real result. The output is named after the source file plus “-watermarked.pdf”; the original is never modified.

Example

CONFIDENTIAL · Centre
45° · 25% · 48 pt · gray

report-watermarked.pdf
All 6 pages carry the watermark
Tile → several stamps per page

The watermark is an image drawn on top of the page, so it cannot be selected or searched. Text direction follows the text itself, not the interface language. The PDF title and metadata stay as they were; the output name is the source name plus “-watermarked.pdf”.

Rules, limits and known issues

• Nothing is uploaded: the PDF is read with the File API and watermarked in this tab. The page sends no network request, writes nothing to storage and keeps no history — a reload starts empty.
• Text watermarks only. Image and logo watermarks are not supported.
• The watermark is a transparent raster image drawn on top of the page. It cannot be selected or searched, and it sits above the existing content rather than behind it.
• One watermark style is applied to every page. Page ranges, different text per page and underlays are not supported.
• Two layouts: centred or a tiled grid. There are no corner presets and no drag-to-position; the watermark is centred on the page.
• Existing watermarks are not detected. Running the tool on an already watermarked file adds another watermark; the original is not removed.
• Watermark text is not translated automatically — it is drawn exactly as typed. Text direction follows the first strong character, so Arabic and Hebrew are shaped right-to-left even in an English interface.
• Rendering uses fonts installed on your device. Unusual symbols or emoji may look different from device to device, and there is no font upload. Long text shrinks to fit the page; tiled spacing is automatic and cannot be tuned.
• Adding a watermark changes the bytes, so digital signatures are no longer valid. PDF/A, PDF/X and other conformance markers are not guaranteed to be preserved.
• Password-protected PDFs are rejected — remove the password and save a fresh copy first. Severely malformed PDFs are not repaired.
• The output name replaces path separators, control characters and reserved characters with “-”, trims the ends, cuts long names and appends “-watermarked.pdf”; the source file itself is never modified.
• Limits: one PDF, 50 MB and 2,000 pages. Larger files are rejected. Files over 20 MB or 300 pages show a “may take a few seconds” hint, and stamping runs on the main thread, so the tab can feel busy while it works.
• The paper preview is an illustration, not a render of your page. Check the real result with “Preview” or by downloading the PDF.

Related tools

Other document tools that also run entirely inside this tab.