A watermark marks a document’s status so it survives being printed, photographed and forwarded. DRAFT across a proposal stops someone quoting the wrong version back at you; CONFIDENTIAL across a report makes the handling rules obvious to anyone who picks up a stray printout.
The text you type is drawn onto a transparent canvas, rotated thirty degrees, and embedded into every page as a PNG image. Rendering through a canvas rather than a PDF font is what lets the watermark be written in any script — Korean, Japanese, Chinese, Cyrillic and Arabic all work, where the standard PDF base fonts would fail. The stamp is centred and sized to ninety percent of the page’s shorter edge, so it lands consistently on portrait and landscape pages alike.
The watermark is composited into the document inside your browser. Neither the source file nor the marked version is uploaded anywhere.
| Setting | Value | Effect |
|---|---|---|
| Small | 48 pt text | Discreet; fits longer phrases without crowding |
| Medium | 76 pt text | The default — clearly visible, still readable underneath |
| Large | 110 pt text | Impossible to miss; best for short words like DRAFT |
| 10% opacity | Very faint | Visible on screen, nearly invisible in a photocopy |
| 20% opacity | Balanced | Reads clearly without obscuring the text underneath |
| 40% opacity | Strong | Dominant; will interfere with reading dense pages |
Medium at 20% suits almost every document. Go to Large at 40% only when the point is to discourage the file from being used as if it were final.
A watermark is a deterrent and a label, not a security control. It is drawn on top of the page content, and someone with a PDF editor can remove the image layer. It does not encrypt the document, does not stop copying and does not prevent printing.
What it does well is make provenance and status travel with the file. A screenshot of a watermarked page still carries the mark; so does a photocopy, a fax and a photograph taken on a phone. That is usually the actual requirement.
Yes. The text is rendered to a canvas using the system font stack before being embedded, so Korean, Japanese, Chinese, Cyrillic, Greek and Arabic all display correctly — unlike watermarks drawn with the PDF base fonts.
Yes, every page of the loaded document gets the same stamp, centred and rotated thirty degrees.
Yes, with a PDF editor. A watermark is a visible label, not a security measure. It does not encrypt the file or prevent copying.
Not currently. The stamp is dark slate grey at your chosen opacity, rotated thirty degrees, which reads well on white pages without obscuring the text beneath.
At 10% and 20% opacity the underlying text remains comfortably readable. 40% is deliberately dominant and will interfere with dense pages.
No. The watermark canvas is built and embedded by pdf-lib in your browser, and the result is written directly to your downloads.
