A watermark is text laid over a page to say something about the document as a whole: that it is a draft, that it is confidential, that it belongs to a particular company, or that it is a sample. People see it every time they view or print the page, which makes it one of the simplest ways to label a file. This tool places a diagonal text watermark on every page of a PDF without any desktop software.

Adding a watermark

1. Upload the PDF.
2. Type the text into Watermark Text, for example CONFIDENTIAL or your company name. If the box is empty, the word WATERMARK is used.
3. Set Opacity with the slider. It is shown as a percentage and starts at 30 percent. Lower values are more subtle.
4. Set Font Size in points. The default is 48.
5. Press Add Watermark. The result downloads as watermarked.pdf.

How the watermark is drawn

The text is set in bold Helvetica, in mid-grey, and rotated 45 degrees so that it runs from the lower left to the upper right. Its starting point is just left of the page centre and the text runs diagonally upward, so a long word sits slightly above and to the left of the exact middle. It is drawn on top of the existing content with the opacity you chose, so the page remains readable underneath. The same text, size and opacity are applied to every page; you cannot target some pages only. To watermark part of a document, split it, watermark the part you want, and merge the pieces back together.

Choosing good settings

Higher opacity makes the mark harder to miss but harder to read through. A level between 15 and 35 percent usually works for text-heavy pages. On pages with images or dark backgrounds, try a slightly higher value and view the result.

Text length and page size

The tool measures the width of the text to centre it, but it does not shrink text to fit. A long phrase at a large size can run past the edges of a small page, and the ends will be cut off. As a rough rule, a word of up to about 12 letters fits an A4 or Letter page at 48 to 60 points. For longer text, reduce the size or shorten the wording. Check at least one page of the result, including any page with a different size or orientation.

What a watermark does and does not do

A watermark is a visible label. It discourages casual misuse and makes the origin or status of a copy obvious, which helps when a file gets forwarded. It does not stop anyone from copying, printing or editing the file. A determined person can remove a flat text watermark with PDF editing software, and the tool does not add passwords, encryption or permissions. If you need to restrict a file, use a dedicated protection tool; if you need to prove authenticity, use a proper digital-signature service.

Practical uses

• Stamping DRAFT on a contract while it is still under negotiation.
• Marking price lists and quotations as CONFIDENTIAL before emailing them.
• Adding a company name to portfolio samples shared with prospects.
• Labelling exam papers or training material as COPY.
• Marking a preview of a paid document as SAMPLE.

Tips

1. Keep the unwatermarked original, since you cannot undo the stamp.
2. Watermark last, after reordering, cropping and numbering.
3. Test with a short document to settle opacity and size, then run the full file.
4. Use all capitals for status words, which read as a label rather than a title.
5. If printing, test a page in greyscale; light marks may disappear on some printers.

Privacy

The stamping is done in your browser by a PDF library. The file is not uploaded.

Frequently asked questions