Free Online PDF Watermarker (Add Text Watermarks)
Stamp custom text watermarks across PDF pages with opacity controls.
How It Works & Calculation Method
Protecting intellectual property, indicating draft revisions, and safeguarding proprietary business presentations requires visible watermarks that deter unauthorized distribution.
Our client-side PDF Watermarker applies semi-transparent vector text stamps across all document pages locally in your browser memory, ensuring your confidential records never touch external servers.
Type your desired watermark text, select diagonal or horizontal orientation, and adjust opacity and color.
The tool calculates page dimensions and draws rotated vector text across each page stream losslessly.
Mathematical Formula
Watermark Stamp = Centered vector text at angle θ (typically 45°) with opacity α (0.05 to 0.80)Worked Example: Stamping 'CONFIDENTIAL' on an NDA
A startup founder watermarks an investor pitch deck before sharing with external venture partners.
Common Pitfalls to Avoid
- •Setting opacity too high (above 50%), making the underlying contract text difficult to read.
- •Using third-party cloud upload services for confidential intellectual property.
- •Forgetting to inspect the full-size view to verify watermark readability.
Who This Tool Is For
- •Founders and executives sharing confidential pitch decks and financial forecasts.
- •Legal counsel marking draft contracts and settlement proposals.
- •Photographers and authors protecting preview copies of portfolios and manuscripts.
How to Use the Watermark PDF
Select PDF
Choose the PDF document you want to watermark.
Configure Stamp
Enter your text, choose opacity, color, and angle.
Download PDF
Save your watermarked document to your device.