Add Watermark to PDF Online Free

Upload your PDF document into the watermark workspace. Choose a quick preset like 'CONFIDENTIAL' or enter your custom stamp text, then adjust the font size, color, opacity, and rotation. Preview your changes in real time on Page 1, then click 'Watermark & Save PDF' to instantly download your stamped file.

No. Toolhast uses native ISO 32000 vector text injection powered by `pdf-lib`. Unlike inferior tools that convert PDF pages into compressed bitmap images, our engine preserves all underlying vector fonts, crystal-clear typography, embedded raster photography, and interactive hyperlinks without introducing resolution loss, pixelation, or visual compression artifacts.

Yes. Toolhast provides a granular opacity slider ranging from 5% (very subtle background watermark) to 85% (bold foreground security stamp). By default, the opacity is set to 25%, ensuring that the watermark is clearly visible to readers while keeping your document's underlying body text completely legible and easy to read.

Yes. You can choose to stamp all pages, only odd pages, only even pages, or specify a custom page range such as '1-3, 5'. This is especially useful for stamping cover sheets, executive summaries, or sensitive contract exhibits without cluttering blank separator pages or published appendix sections.

Simply click the '45° Diagonal' rotation button in the customizer toolbar. Toolhast automatically calculates the trigonometric center of the rotated text bounding box, ensuring your watermark stretches gracefully across the diagonal center of your document pages just like official legal discovery, confidential draft, and government security stamps.

Yes, 100%. Toolhast executes all font embedding, coordinate mathematics, and PDF stream modifications directly inside your local web browser using client-side JavaScript. Your confidential business agreements, legal contracts, tax records, and medical files are never uploaded, stored, or transmitted to any external server or third-party cloud infrastructure.