Stamping "CONFIDENTIAL" or "DRAFT" across a document you're about to share is a common enough need that most free PDF sites offer some version of the tool — the friction shows up around the edges. Smallpdf's watermark tool sits behind the same two-tasks-per-day free cap as the rest of its suite, according to comparison reviews, and some of its free conversions add Smallpdf's own branding to the output, which defeats the point if your goal was a clean, custom mark. iLovePDF processes the file on its servers before returning it, per its privacy policy, which is an odd trade-off when the whole reason you're watermarking is that the document is sensitive in the first place. Adobe's free web version, per third-party comparisons, offers a handful of preset positions rather than letting you dial in your own opacity, size and angle.
Add a text watermark to a PDF in your browser, with no upload
Type your own text — "CONFIDENTIAL", "DRAFT", a case number, anything up to 60 characters — and it's drawn directly onto every page using a PDF library loaded on the page itself. The file never leaves your device, which matters most exactly when the watermark's purpose is to protect something sensitive. No account, no branding of ours is added, and no daily limit.
Single centered watermark vs. tiled diagonal: which to use
A single centered mark is quick and unobtrusive, sitting once in the middle of the page — good for an internal draft nobody's likely to screenshot around. Tiled diagonal repeats the text in a grid across the entire page, which is much harder to crop out of a photocopy, screenshot or cell-phone photo of the screen, making it the better choice for anything meant to discourage unauthorized reuse.
Controlling watermark opacity, size and angle
The opacity slider runs from a subtle 10% up to a bold 80%, size from 12pt to 120pt, and rotation from flat (0°) to a full 90° turn — the classic diagonal "CONFIDENTIAL" stamp sits around 45°, which is the default. All three update live as you adjust them, so you can preview the balance between visible-enough and not obscuring the text underneath before you download.
Watermarking a password-protected or scanned PDF
An encrypted file can't be read without its password — remove the password in the app that created it, then add the file here. Because the watermark is drawn as a text layer on top of the existing page content rather than replacing it, scanned pages (which are really just embedded images) take a watermark exactly the same way as a text-based PDF does.
Try the PDF Watermark Adder → · Want to clean up who's listed as the file's author first? See the PDF Metadata Editor.
Sources: makerstack, Smallpdf review (2026); PixelTools, "Smallpdf vs iLovePDF: Free Limits & Pricing" comparison (2026); iLovePDF privacy policy, file retention statement; ihatepdf, "ihatepdf vs iLovePDF vs Smallpdf vs Adobe" comparison (2026).
