Stamp a diagonal text watermark such as CONFIDENTIAL across every page, processed locally with pdf-lib in your browser, your document never leaves your device.
Your PDF is processed locally with pdf-lib in your browser; your document never leaves your device. Nothing is uploaded to any server.
Up to 40 characters. The text is stamped diagonally at the center of every page.
Lower opacity keeps the text underneath readable while still marking the document.
Working…
Watermarks state ownership and sensitivity at a glance: CONFIDENTIAL on a contract draft, DRAFT on a proposal that is still under review, or DO NOT COPY on a licensed handout. This tool stamps your text on every page of a PDF in one pass. The mark is drawn diagonally at 45 degrees across the center of the page using the standard Helvetica font, so it needs no extra embedding and works in every PDF reader.
Three controls tune the look. Font size ranges from a discreet 36 points to a banner-like 90 points. Color can be gray, black, or red. Opacity controls how strongly the mark sits over the page content; 15% is enough to be visible on every page while leaving body text perfectly readable, while 50% makes the status impossible to miss. The watermark position is computed per page from that page's own dimensions, so mixed-size documents are stamped consistently.
Everything happens locally in your browser; your document never leaves your device, which is exactly what you want when marking documents confidential. Related jobs: turning pages that scanned sideways (PDF Rotate), numbering the pages (PDF Page Numbers), or joining files before stamping them (PDF Merge).
The watermark becomes part of each page content stream, so there is no simple toggle to remove it; that is the point of a watermark. Anyone determined can still edit a PDF with professional tools, so treat this as a visual deterrent rather than copy protection.
The tool uses Helvetica, one of the 14 standard PDF fonts. It is referenced rather than embedded, which keeps the file size almost unchanged and guarantees identical rendering in every PDF reader.
For most documents 15% is ideal: the mark is visible on every page but body text stays fully readable. Use 30% for internal drafts and 50% when the status must be impossible to miss, accepting that text under the mark is harder to read.
The text is drawn once per page, rotated 45 degrees and centered. At the large 90 pt setting a short word like DRAFT stretches across most of the page; longer phrases up to 40 characters fit because the font size does not shrink them. On very small pages the mark may extend past the edges, which reads as a classic security stamp.
Yes. Scanned pages are images, and the watermark is drawn on top of the image at the chosen opacity. The original scan underneath is not modified, so the mark never degrades the scan quality.