What a PDF watermark is
A watermark is text or a mark placed across a page's content to signal its status, such as DRAFT, CONFIDENTIAL, or COPY. It is meant to be seen without being so heavy that the underlying page becomes unreadable, which is why watermarks are usually semi-transparent and set at an angle.
This tool adds a text watermark using the PDF library's drawing functions. It writes your text onto every page in bold Helvetica, in a medium grey, rotated 30 degrees upward from left to right, centered horizontally around the middle of the page. The text is added as part of the page content, so the original pages are not rasterized and their own text remains as it was.
When to watermark a PDF
Typical uses are marking a document as a draft while it is still being reviewed, labeling a copy as confidential before sending it to a client, or stamping a sample so it is not mistaken for a final version. Some people also add a name or reference to a file so that a stray copy can be traced to the person it was shared with.
A watermark is a visible label, not a lock. It does not stop anyone from reading, copying, or printing the document, and it is not the same as password protection. It is a clear signal about how the file should be treated.
Related finishing tools on this site include Add Page Numbers and Sign PDF, which work well in sequence with a watermark.
How to add a watermark to a PDF
- Drag your PDF onto the upload area, or click it to choose a file.
- In Watermark text, type what you want to stamp. The default is CONFIDENTIAL.
- Set Opacity with the slider, from 5% to 100% in 5% steps. The default is 30%.
- Set Size with the slider, from 12 to 100. The default is 48.
- Click Add watermark. When processing finishes, a Download button appears.
- Click Download to save the file as watermarked.pdf.
- Use Start over to load a different PDF.
The work is done in your browser and the file is not uploaded.
Choosing settings and avoiding problems
The watermark has a fixed grey color, a fixed 30 degree angle, and one position near the center, so the controls are limited to the text, the opacity, and the size. There is no preview before you apply it, so if the result is not right, change a setting and click Add watermark again, then download the new version.
Text length matters. Longer text at a large size can run beyond the edge of a narrow page, so for long phrases lower the size. Pages with different dimensions are each centered on their own, but one size applies to every page.
Because the font is a standard built-in one, stick to plain letters and numbers. Unusual characters may not be supported and can cause an error. The tool also needs a valid PDF that is not encrypted, and it will say so if loading fails. Finally, remember that anyone with PDF editing software may be able to remove a watermark, so do not rely on it for security.