Add a watermark to PDF

Why add a watermark to a PDF?

A watermark tells anyone who opens the file what its status is and who it belongs to. DRAFT stops an early version being mistaken for the final one, CONFIDENTIAL reminds recipients not to forward it, and a logo or client name makes leaked copies traceable. Photographers and designers use a faint, tiled watermark on proofs so the work can be reviewed but not reused.

What watermark options are available?

You can stamp either text or an image, place it at one of nine positions or tile it across the page, and control size, color, opacity and rotation. Every change is reflected immediately in the preview, which is rendered from your own document with pdf.js, so the placement can be judged against real content rather than a blank page.

• Text in sans, serif or monospaced style, bold or regular, in any color.
• Images such as logos or signatures, sized as a percentage of the page width.
• Opacity from 5 to 100 percent, and rotation from -90° to 90° with 45° presets for diagonal stamps.
• Nine anchor positions, or a staggered tiled pattern that covers the whole page.
• All pages or a custom range, for example only the pages after a cover sheet.

Which watermark settings work best?

For documents people need to read, keep opacity around 15 to 30 percent and use light gray or red, because a heavy watermark makes printing and scanning worse. The table lists starting points for common cases. Preview a page with dense text or a large table before applying, since that is where legibility suffers first.

How is the watermark applied to the file?

The watermark is written into each page's content stream, the sequence of drawing instructions that ISO 32000-2 defines for a PDF page, using the same layout math as the preview. Page rotation and crop boxes are taken into account, so what you see is what you get. It is not stored as a separate annotation that a reader could select and delete.

The original pages are not rasterized, which means text stays sharp and searchable. File size barely grows for text watermarks, and an image watermark is embedded once and reused on every page, so even a 300-page document gains little more than the size of the logo. To number pages as well, run the result through Add Page Numbers.

Does a watermark protect a PDF from copying?

No, a watermark deters misuse and marks ownership, but it does not stop copying, printing or editing on its own. It sits on top of the page, so it also covers images and can reduce the legibility of dense tables at high opacity. A determined person with editing software can remove it, although a tiled diagonal pattern takes far more effort than a single corner stamp.

For documents that must not be altered, add a password to the watermarked file with Protect PDF. For true removal of confidential details, use Redact PDF before sharing, because a watermark hides nothing. Text watermarks use the built-in PDF fonts, so characters outside Western European alphabets need an image watermark instead.