How to use the Watermark PDF tool
- Choose your PDF.
- Type the watermark text and choose whether it appears once in the centre or repeated across the page.
- Adjust font size, opacity, angle and colour. A diagonal 45 degree stamp at 25 percent opacity is a classic starting point.
- Press Add watermark, check the preview of page 1 and download the result.
Worked example: CONFIDENTIAL on a 10-page Letter document
terms.pdf has 10 US Letter pages, 612 points wide. You keep the defaults: CONFIDENTIAL, bold, 60 point, 25 percent opacity, 45 degrees, dark red, one centred stamp.
- In 60 point bold Helvetica the word is about 447 points long, a little over 6.2 inches, so it spans most of the page diagonal without touching the edges.
- Every one of the 10 pages gets the stamp, centred on the page, and the file still has 10 pages.
- The shorter word DRAFT at the same size is about 203 points long, so you may want a larger size for it.
The download is named terms_watermarked.pdf.
Getting a readable watermark
A good watermark is visible but never hides the content. Keep opacity between 15 and 35 percent, use a mid-tone colour such as grey or dark red, and choose a size that spans most of the page width for a single centred stamp. Tiled mode repeats a smaller mark across the whole page, which is harder to crop out and suits drafts and previews. The preview shows page 1 of the finished file so you can adjust and run it again before saving.
What a watermark does and does not do
The text is drawn on top of each page as ordinary page content. It discourages casual reuse and labels a document clearly, but it is not security: anyone with a PDF editor can remove it. For access control you need encryption, which this browser tool does not provide. Text uses the built-in Helvetica font, so Latin letters, digits and common punctuation work; emoji and other scripts are not supported. Rotated pages are handled so the watermark keeps the angle you chose on screen.
Your files stay on your device
The watermark is drawn by a background worker in your own browser and the preview is rendered locally. The document stays on your device from start to finish, which is exactly what you want when the page is stamped Confidential.
Frequently asked questions
Can I use an image or logo as a watermark?
Not in this tool; it adds text only.
Can the watermark be removed?
Yes, by someone with PDF editing software, because it is ordinary page content. It deters casual copying but is not protection. To hide information for good, use Redact PDF.
Can I watermark only some pages?
The watermark is applied to every page. Extract or split the pages you want first if you need a partial result.
Why is my text rejected?
The built-in font supports Latin characters. Emoji and non-Latin scripts cannot be drawn, so the tool shows a message instead of producing garbled output.
Will it change the quality of my pages?
No. The original page content is kept and the text is added on top.