Stamp text or a logo on every page, or only on the pages you choose: single mark, nine positions, or tiled across the page. Schematic live preview. Nothing is uploaded.
The mark is drawn on top of the page and is not a security feature: anyone with a PDF editor can remove it. Text uses built-in fonts, so only basic Latin letters and digits work; for other languages use the logo option with an image of the text. The preview is schematic (a blank page), not a render of your pages. Password-protected PDFs must be unlocked first.
Is my PDF uploaded? No. The watermark is added locally in your browser.
Can I mark only some pages? Yes. Type the pages, for example 1-3, 5, 8- (8 to the end).
Can I use a copy for a visa or bank? Writing COPY or the purpose on a document copy is common practice, but check what the receiving office accepts.
Why do some letters fail? The built-in fonts support basic Latin letters only. Accented or non-Latin characters are rejected with a message.
Related: add page numbers, merge PDF, watermark an image.
Informational tool, not legal or tax advice.