Add watermark is a free tool that runs entirely in your browser. Diagonal text watermark across every page. A quick edit like this saves you from launching heavyweight desktop software just to make one small change. Because everything happens locally with pdf-lib and pdf.js, your files are never uploaded to a server — Add watermark works instantly, even offline, and keeps every document completely private, with no account, no watermarks and no file-size limits.
How to use Add watermark
- 1Open the Add watermark tool and drop in your PDF, or click to choose it.
- 2Set your options — Text, Opacity % — then press Run.
- 3Download your result. The whole thing happens on your device, so your PDF never leave your browser.
100% private — nothing is uploaded
Unlike most online PDF tools, Add watermark never sends your PDF to a server. Everything is computed locally in your browser with JavaScript, so your documents stay on your device. There's no account, no watermark and no file-size limit — and it even keeps working with your Wi-Fi switched off.