Add Watermark to PDF
Processed in your browser. The document is never uploaded.
Choose a PDF, set the text, then apply.
The PDF watermark tool stamps text diagonally across every page of a document, with adjustable opacity, size and rotation. The watermark is drawn into the page content in your browser, so the document is never uploaded, which matters, since watermarking is usually applied to something confidential.
How it works
- The text is drawn in Helvetica Bold, one of the 14 fonts every PDF reader includes, so no font has to be embedded and the file barely grows.
- Rotation is applied about the text origin, and the starting position is offset by half the rotated text width so the result stays centred.
- Opacity is applied as a graphics state on the text itself rather than as a transparent overlay layer.
- Every page in the document gets the same watermark, sized in points where 72 points is one inch.
The watermark is added to the page content stream, not as an annotation. That makes it harder to remove than a comment or a stamp annotation, but it does not make it permanent, see the note below.
Examples
A standard draft stamp
Text
DRAFT
Opacity
20%
Size
60pt
Rotation
45°
Result
Every page stamped diagonally in light grey
20 percent opacity is legible without obscuring the text underneath. Above about 35 percent the document becomes hard to read.
A horizontal confidential marking
Text
CONFIDENTIAL: DO NOT DISTRIBUTE
Rotation
0°
Size
24pt
Result
A horizontal band across the middle of each page
Longer text needs a smaller size to fit the page width. At 0 degrees the centring calculation is exact, since there is no rotation to compensate for.
Limits worth knowing
A visible watermark deters casual redistribution and records intent. It is not encryption, not redaction and not access control, and it should never be the only protection on something genuinely sensitive.
Frequently asked questions
Can the watermark be removed?
By anyone with the right tools, yes. It is drawn into the page content stream rather than added as an annotation, so it is not a one-click removal, but PDF content is editable and a determined person can strip it. Treat a watermark as a marking of intent, not as a security control.
Why does my encrypted PDF fail?
Because a password-protected PDF cannot be modified without the password, and this tool does not prompt for one. Remove the protection first if you have the password; if you do not, the document is not yours to watermark.
Why is the watermark not perfectly centred on rotated text?
Because rotation happens about the text origin rather than its centre, so the starting point has to be offset by half the rotated width. The tool does that calculation, but very long text at steep angles can still extend past the page edge, reduce the font size in that case.
Does it increase the file size much?
Barely. Helvetica Bold is one of the 14 standard PDF fonts that every reader already has, so nothing is embedded. The addition is a few hundred bytes per page regardless of document length.