Add Watermark: how it works
To watermark a PDF, open the Add Watermark tool, add your file, type your text, and adjust the angle and opacity before downloading. The watermark is applied in your browser and the file is never uploaded.
How to use Add Watermark
- Open the Add Watermark tool and add your PDF.
- Enter the watermark text and set angle and opacity.
- Download the watermarked PDF.
In your browser vs. uploading to a server
Best for marking documents as Draft or Confidential privately. Text watermarks are applied across every page.
Frequently asked questions
How do I add a watermark to a PDF?
- Open the Add Watermark tool, type your text, adjust angle and opacity, and download; the watermark is stamped across all pages in your browser.
Are my files uploaded to a server?
- No. PDFER runs entirely in your browser using WebAssembly and JavaScript. Your files are read into memory on your device, processed locally, and never sent to PDFER or any third party. Closing the tab or leaving the tool erases them from memory.
PDFER is a privacy-first PDF toolkit built by Kiril Urbonas. Every tool runs entirely in your browser — see our security model and privacy policy.