Watermark Tool - Free Online PDF Tool

Stamp custom text watermarks onto any PDF by adjusting font size, opacity, rotation, and position. Choose between a centered overlay, four corner placements, or a tiled grid pattern that repeats across every page. Built with pdf-lib, all processing happens locally in your browser, keeping sensitive documents private while adding visible stamps like CONFIDENTIAL or DRAFT.

How to Use

1. Upload the target PDF file using the file input field.
2. Set the watermark text and customize font size, opacity, rotation, and position.
3. Click Apply Watermark to process every page of the document.
4. Download the watermarked PDF when the processing finishes.

Key Features

• Custom text watermarks
• Adjustable opacity
• Rotation angle control
• Tiled grid pattern
• Corner placements

Frequently Asked Questions

Does this tool upload my PDF files to a remote server?

No, the tool runs entirely in your browser using pdf-lib. Your files are processed locally, ensuring your sensitive data stays on your device and is never transmitted to external servers.

What is the difference between center and tile watermark positions?

Center places a single watermark in the middle of each page. Tile creates a repeating grid of watermarks across the entire page surface, ideal for densely stamped backgrounds.

How can I make the watermark text less visible?

Reduce the opacity slider to a low value like 0.1 or 0.2. This creates a faint overlay that marks the document without completely obscuring the underlying text.

Launch Watermark Tool

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Maintained by Huang Bin · Last updated October 3, 2026