How to Add a Watermark to a PDF Online

Upload your file to the Watermark tool, type the watermark text and set opacity and font size. The text is drawn in grey across the centre of every page, horizontally, on top of the existing content. Nothing is deleted from the page.

Download the file and compare a text-heavy page with an image-heavy one. The same setting can look clear on a white page and almost vanish over a dark table or a full-page photograph.

Four opacity levels are available. The two lightest settings suit drafts where the underlying text must stay comfortable to read. The medium setting works when the mark should be impossible to miss. The strongest setting is for samples and specimens, where the status matters more than the readability.

Font size defaults to 48 points. Longer text spreads further across the page, so short phrases sit more neatly at that size. If you need a full sentence, reduce the size, otherwise the ends of the watermark can run into the page edges.

Single-word status markers such as CONFIDENTIAL, DRAFT, SAMPLE and COPY are the most common choice. A company name identifies the source of a document. If you are sending the same file to several people individually, putting the recipient name in each copy lets you trace where a leaked file came from.

A date is useful too, especially for contracts and quotations that go through many rounds, because it removes any doubt about which version someone is holding. Check the first output visually before producing a batch.

Watermarking discourages misuse; it does not prevent it. Anyone who opens the file can still read, copy and screenshot the content. To stop unauthorised people opening the document at all, use PDF Encrypt and set a password.

A watermark also does not hide anything. To genuinely remove identifiers, amounts or contact details from a file, use PDF Redaction. Because the watermark becomes part of the page content, keep the original file if you may later need a clean version.