This tool stamps a diagonal or tiled text watermark and/or running page numbers directly onto every page of a PDF, right in the page content stream, not as a floating annotation you can strip out by accident. It renders a live preview of page one so you can check size, opacity, and position before committing to the whole document, then rebuilds the file client-side and hands you the download.
Since the watermark text is drawn straight into each page's content stream rather than added as a separate annotation layer, it stays in place through normal viewing, printing, and most PDF merges. Someone with a dedicated PDF editor could still select and delete the text object, the same as they could with any other text on the page.
Yes, the position grid and numbering controls let you set a starting number and a format, and you can choose to leave the first page unnumbered so a cover or title page isn't marked.
No. The file is read, modified, and rebuilt entirely inside your browser using client-side PDF libraries, it never leaves your device, which also means it works offline once the page has loaded.