What is a PDF watermark?
A watermark is semi-transparent text or an image overlaid on every page of a PDF. Common uses:
- Marking a document as DRAFT, CONFIDENTIAL, or SAMPLE
- Branding a document with your company name
- Discouraging unauthorised distribution
How to add a watermark to a PDF free
- Open the Add Watermark tool.
- Drop your PDF onto the upload zone.
- Configure the watermark:
- Text: Type your watermark text (e.g. "CONFIDENTIAL").
- Font size: Larger text is more visible; 48pt is a good default.
- Opacity: Lower values are more subtle. 30% is standard for draft marks.
- Rotation: 45° diagonal is the classic watermark style.
- Preview the watermark in the live preview box.
- Click Apply Watermark.
- Download the watermarked PDF.
Tips
- Contrast: Dark text on light backgrounds reads well at 20–30% opacity. Light text may not be visible on white pages.
- Placement: The watermark is centred on each page. Pages of different sizes (A4 vs Letter) are handled automatically.
- Removal: A simple text watermark can be removed by someone with the right tools. For security, also encrypt the PDF so it cannot be easily edited.
Is this really done in my browser?
Yes. pdf-lib (a WebAssembly library) draws the text directly onto each page of your PDF without uploading it. The file never leaves your device.
Can I watermark only some pages?
Currently the watermark is applied to all pages. Page-level control is on the roadmap.