What PDF Watermark does
The watermark tool stamps a line of text — CONFIDENTIAL, DRAFT, SAMPLE, a company name, a recipient's email — on every page of a PDF. You choose the wording, the font size, the opacity, and whether it runs diagonally across the centre or sits along the top or bottom edge. The text is drawn as real vector text, so it prints crisply and adds only a few bytes per page. The rest of the page is untouched, and the file never leaves your browser.
Choosing a position
| Position | Look | Best for |
|---|---|---|
| Centre (diagonal) | Large text across the middle of the page at 45° | DRAFT, CONFIDENTIAL, SAMPLE, NOT FOR DISTRIBUTION — hard to ignore or crop |
| Top | A single line along the top margin | Document status, version, or classification labels |
| Bottom | A single line along the bottom margin | Copyright notices, recipient name, download date |
The diagonal stamp is the conventional choice for status marks because it overlaps the content and survives cropping. The edge positions are better for identifying information that should be readable without obscuring the page.
Settings that work
- Opacity: 0.15–0.3 for a diagonal stamp that leaves the text underneath readable; 0.5–1.0 for an edge label that must be legible on its own.
- Font size: 60–100 pt for a diagonal stamp on A4 or Letter; 10–14 pt for edge labels.
- Wording: short and uppercase reads best when rotated. One or two words for diagonal marks; a short sentence is fine along an edge.
- Colour: the stamp is drawn in grey at the opacity you set, which reads on both white pages and photographs.
- Check the first and last pages after stamping — a diagonal mark can land awkwardly on a page that is mostly a single image.
Common uses
- Drafts and versions — so a superseded copy is never mistaken for the final.
- Confidential documents — legal, HR and financial files marked before circulation.
- Samples and previews — a chapter, report or design sent before purchase.
- Personalised copies — the recipient's name or email on each copy discourages forwarding and identifies the source of a leak.
- Copyright and attribution — a footer line on teaching materials, photography portfolios and e-books.
- Scans of originals — “COPY” across a scanned certificate or ID sent to a third party.
What a watermark does and does not protect
A visible watermark is a deterrent and an identifier, not a lock. It stops a document being passed off as final or original, and it makes leaks traceable when personalised. It does not prevent copying: the stamp is drawn into the page content, and anyone with a PDF editor can remove it with some effort, more easily for edge labels than for a diagonal mark over text. For genuine access control you need encryption or a rights-management system; for tamper evidence you need a digital signature. Combine the watermark with a copy-restriction owner password in a desktop tool if the stakes are high.
Text is drawn, not pasted as an image
The tool embeds a standard font and writes the text into each page's content stream with the chosen rotation and opacity (using a transparency graphics state). Because it is vector text, it stays sharp at any zoom or print resolution and is picked up by text search — which is useful for finding watermarked copies later.