No. Everything happens in this browser tab, on your own device. There is no upload endpoint and no server-side processing, so the file never leaves your machine — you can disconnect from the network after the page loads and it still works.

Can a watermark be removed by someone else?

A watermark is ordinary page content, so a determined person with the right tools can strip it. It marks a document, it does not protect one — for that, use a password.

Add a watermark to a PDF

Add diagonal text across a page range, at whatever size and opacity suits. The watermark is added as an ordinary editable object, so you can move or delete any individual one before saving.

How to do it

Open the PDF.
Open the watermark panel and type your text.
Set the size, angle and opacity, and choose a page range.
Download.

Why nothing is uploaded

Most online PDF tools work by sending your file to a server, editing it there, and sending it back. That means contracts, medical records, bank statements and passports all end up on someone else's machine, and you are trusting a privacy policy about what happens next.

This editor does the work in your browser instead. The PDF is read by this tab, rendered with pdf.js and written back out with pdf-lib, both running as ordinary JavaScript on your own device. There is no upload endpoint, because there is no server doing any of this. Once the page has loaded you can disconnect from the network entirely and everything still works.

Questions

Is my file uploaded?: No. Everything happens in this browser tab, on your own device. There is no upload endpoint and no server-side processing, so the file never leaves your machine — you can disconnect from the network after the page loads and it still works.
Can a watermark be removed by someone else?: A watermark is ordinary page content, so a determined person with the right tools can strip it. It marks a document, it does not protect one — for that, use a password.

Related tools

Add page numbers to a PDF — Number the pages of a PDF, with headers and footers, entirely in your browser.
Password-protect a PDF — Add a password and set permissions on a PDF. AES-256 encryption applied in your browser — the document and the password never leave your device.
Merge PDFs — Combine several PDFs into one, in your browser. Nothing is uploaded, there is no account, and there is no page limit.
The full editor — annotate, sign, fill forms, redact, OCR and more.

Part of messy-ui. Free, open source and account-free — see also the countdown timer.