How to add a watermark to a PDF
- Drop your PDF on the dashed box, or press Enter on it to choose a file.
- Type Watermark text (up to 60 characters) or press a preset: CONFIDENTIAL, DRAFT, SAMPLE, DO NOT COPY or VOID.
- Set Font size (20 to 120 pt), Opacity (5% to 100%), Color and Rotation (-90 to 90 degrees). Defaults: 60 pt, 15%, gray #888888 and -45 degrees, which rises toward the right.
- Choose Position (Center, Top or Bottom) and Apply to (All pages, First page, Last page or Specific pages such as
1,3,5-8). - Select Add watermark, then Download watermarked PDF. Changing a setting afterward hides the download button, so you never save a stale file.
How the watermark is placed
The tool draws your text in Helvetica Bold on top of each chosen page and sets opacity through PDF transparency. It reads each page's visible area (the CropBox, else the MediaBox) and page rotation, so the watermark stays upright on sideways scans. The middle of the text goes on a target point: Center is the middle of the page, Top is 85% of the page height and Bottom is 15%, pulled back if the text would leave the page. Text that would exceed 92% of the page width or height is scaled down for that page. Page boxes and rotation are defined in the PDF 1.7 specification (ISO 32000-1); the drawing uses pdf-lib 1.17.1.
Worked example with the default settings
On a US Letter page (612 x 792 pt), the letters of CONFIDENTIAL in Helvetica Bold add up to 7,444 units per point of font size, so at 60 pt the word is 446.6 pt wide. Tilted 45 degrees it covers about 346 x 346 pt, well inside the 563 x 729 pt the tool allows, so nothing is shrunk. Its center lands at 306, 396 pt, the middle of the page. The line under the preview reads: "Letter page, 612 x 792 pt. The text is 446.6 pt wide and covers 346 x 346 pt at this angle, centered on the page." At 120 pt the footprint would be about 693 pt across, so the tool reduces the text to 97.5 pt and says so.
Limits and edge cases
- One line of text in one color. For pictures use Image Watermark.
- Only Western European characters work, because PDF's built-in fonts lack other scripts.
- Encrypted PDFs are refused. Unlock them with the PDF Password Remover first.
- In a specific-pages list, an open end such as
5-runs to the last page. - Afterward, add numbers with the PDF Page Numberer or shrink the file with the PDF Compressor.
Frequently asked questions
Can someone remove the watermark from my PDF?
Yes, with effort. The text becomes ordinary page content, so a PDF reader cannot hide it, but anyone with a PDF editor can delete it or paint over it. Treat a watermark as a label that discourages casual reuse, not as security.
Why is my watermark smaller than the font size I picked?
The tool keeps the rotated text inside 92% of the page width and height. Long text, a big font size or a small page makes it lower the size on that page. The line under the preview shows the final size.
Can I use Chinese, Arabic, Cyrillic or emoji as the watermark?
No. The tool draws Helvetica Bold, the font every PDF reader has, which covers Western European letters, digits and common punctuation such as the euro sign. It names any other character and waits for you to remove it.
Can I put the watermark behind the page text instead of on top?
No, it is added after the page content, so it sits on top. At the default 15% opacity the text underneath stays readable. For solid backgrounds or scans, lower the opacity.
Can I watermark a password-protected PDF?
Not directly. Encrypted files cannot be changed without corrupting them, so the tool refuses them. Remove the password first with the PDF Password Remover, then add the watermark.
Sources: PDF 1.7 specification (ISO 32000-1:2008); pdf-lib API documentation.