Add a Watermark to PDF — Free, In-Browser (No Upload)

A watermark is a visible deterrent, not a lock

Adding a watermark to a PDF makes casual misuse obvious, not impossible. Anyone with basic PDF tools can obscure the text, crop it out, or reconstruct the page without it. What a watermark genuinely does is make a leak traceable and visible: a DRAFT stamp stops someone from accidentally circulating an unapproved version to the wrong recipient, and a recipient-specific mark (like a customer name or file ID) makes it clear where the document came from if it appears outside your control. Use watermarks for attribution and accountability, not security.

Opacity is your real design decision

The opacity slider runs from 5% to 80%, and this range captures a real trade-off: too faint (5–15%) and the watermark is trivially cropped or overlooked; too strong (70%+) and the document becomes hard to read, defeating the purpose of sharing it. Most use cases land between 20–40%, where the watermark is clearly visible but doesn't interfere with reading. The tool defaults to 22% opacity — a starting point you can adjust per document based on how much visibility you need versus legibility.

Diagonal placement across the center resists removal

The watermark always runs diagonally at a 45° angle across the middle of the page, rotated around the document center. This positioning matters: a corner stamp or header text sits in white space that can be cropped out cleanly, but a diagonal watermark overlaps the actual content, making removal more disruptive. If someone crops the watermark away, they damage the document itself. If you want something less noticeable, adjust the opacity down rather than expecting placement changes.

Honest limits of what this tool can and cannot do

The watermark is drawn as crisp vector text onto every page of your PDF. It applies to all pages at once — there is no way to watermark only a page range or to add different text to different pages. For encrypted PDFs, the password is remembered while you work, so the watermark is applied during export. Scanned PDFs (image-based) can be watermarked just as easily as text PDFs, because the watermark is layered on top regardless of what's underneath. One detail worth knowing: on ordinary pages the watermark is written as real PDF text, so it stays selectable and searchable in the output — which also means a determined recipient can find and strip it more easily than if it were part of the picture. On a page that carries a redaction, the whole page is flattened to an image at export, and the watermark goes into that image with everything else. For related watermarking and protection, see protect PDF and redact PDF.