Watermark PDF

The watermark is drawn as real text into the page's content, not laid over it as an image. The document stays a normal PDF: the existing text is still selectable and searchable, nothing is rasterised, and the file does not balloon. Tools that flatten pages to images to add a watermark destroy the text layer, which makes the document unsearchable and unreadable to a screen reader.

That has an honest consequence worth stating: because it is ordinary page content, anyone with a PDF editor can remove it. A watermark marks a document as a draft, a copy, or not for distribution. It does not protect it, prevent copying, or survive a determined recipient. Treating it as security is a mistake people make with real consequences.

A diagonal stamp is sized to span the page rather than set to a fixed point size, so it looks right on A4, on US Letter and on a widescreen slide without adjustment. Tiling repeats the text in a grid instead, which is harder to crop out of a screenshot and considerably uglier — useful for genuinely sensitive drafts.

Opacity around 15% is the usual choice: clearly legible, and not so heavy that the document underneath becomes hard to read. Anything above about 40% starts competing with the content.

The document is stamped entirely in your browser. Marking something CONFIDENTIAL by uploading it to a stranger's server would be an unfortunate way to start.