Add a Text Watermark to PDF — Free
Stamp a diagonal text watermark on every page of a PDF, with adjustable size and opacity.
This tool places a diagonal line of text across the middle of every page — words like "CONFIDENTIAL", "DRAFT", or "COPY". You choose the text, the font size, and how strong or faint it looks. Thai text is fully supported as well.
How to add a watermark to a PDF (3 steps)
- Open your PDF file.
- Type the watermark text, then adjust its size and opacity.
- Apply the watermark and download the result.
What a watermark does — and what it doesn't
A watermark is faint text laid over the page. It is most often used to discourage misuse of a document, to show that a document is still a draft, or to mark something as a certified copy. The key point: a watermark is a notice, not a lock. It tells readers the conditions attached to a document, but it does not stop anyone from copying the content.
- Showing that a document is an unfinished draft — a good fit. Use "DRAFT".
- Tracing a leaked copy back to its source — it helps. Put the recipient's name or the date in the watermark.
- Stopping people from copying the text — it can't. Use password protection and permissions or flatten the PDF to images.
- Hiding sensitive information — it can't. Use Redact PDF.
Settings that keep both the text and the watermark readable
The usual problem is a watermark so faint nobody notices it, or so heavy it hides the content. Guidelines that work in practice:
- 15–25% opacity suits most documents — clearly visible, while the text underneath stays easy to read.
- 30–40% opacity for documents that need a stronger warning, such as "NOT FOR REFERENCE".
- Font size should be large enough to span the page without running off the edges; 60–90 usually works well.
- Short words work better than long sentences — "COPY", "DRAFT", "SAMPLE", or "DO NOT COPY" read more easily.
- Dense tables call for lower opacity, because numbers crossed by a watermark are easy to misread.
Common watermark text
- Sending a copy of an official document: "CERTIFIED COPY — for [organization] use only"
- Sending a draft to a client: "DRAFT — pending approval"
- Sharing a portfolio or work sample: "SAMPLE — not for commercial use"
- Sending one document to several parties: "For [recipient name] · [date]"
If the same document goes to several people, put each recipient's name in the watermark and create one file per person. If a copy leaks, you will know straight away whose copy it was.
Permanent vs. removable watermarks
The watermark added by this tool is an object inside the PDF, so someone with a PDF editor may be able to remove it. To make it truly permanent, run the file through Flatten PDF afterwards. The watermark then becomes part of the page image — in exchange, the text in the document can no longer be copied (which is sometimes exactly what you want).
Going the other way: if you have a watermarked file that you have the right to use — for example your own document with the wrong watermark — you can try Remove Watermark.
FAQ
Can I use Thai text in the watermark?
Yes. Thai text is fully supported and renders correctly on every page.
Will the watermark cover the content?
You can lower the opacity so the content stays easy to read through the watermark.
Can I watermark only some pages?
The current version watermarks every page. If you need only certain pages, split the file first and then add the watermark.
Can the watermark be removed later?
Someone with a PDF editor may be able to remove it. Flatten the file after watermarking so the watermark becomes part of the page image.