How to use the Watermark PDF tool
- Select your filesClick “Choose Files” or drop them into the box above. Nothing is uploaded — the file is opened locally by your browser.
- Choose your settingsOpen the settings panel to fine-tune the result. The defaults work well for most files.
- Click “Add watermark”Processing takes a few seconds. When it is done, download your file — or all results as a single ZIP.
Why use ConvertMathly?
Files are processed on your device and never uploaded. Close the tab and they are gone.
No account, no daily cap, no queue and no watermark — convert as much as you want.
No waiting for uploads or downloads: results are ready as fast as your device can process them.
Windows, Mac, Linux, Chromebook, iPhone and Android — any modern browser, nothing to install.
Frequently asked questions
Is Watermark PDF free?
Yes. Watermark PDF is free to use as often as you like — no sign-up, no watermark and no file limits.
Are my files uploaded?
No. ConvertMathly processes files directly in your browser, so they never leave your device. This is safer than tools that upload documents to a server.
Does it work with large PDFs?
Yes. Documents with hundreds of pages are fine on a computer; on phones, very large files may take longer.
Does it work on mobile?
Yes — on iPhone, iPad, Android, Windows, Mac, Linux and Chromebook, in any modern browser.