Watermark PDF pages
in your browser.

Stamping text across every page of a PDF

The reasons to watermark a PDF are usually about controlling how a document is read and shared. A draft going out for review needs DRAFT across each page so a reviewer doesn't accidentally treat it as final. A contract sent to a third party needs CONFIDENTIAL so it isn't forwarded casually. A photographer's portfolio needs the studio name on every spread so screenshots still carry attribution. An internal report being circulated for comment needs the date so two readers don't argue over which version they're holding. The job here is small and predictable: type a string, pick where it goes and how loud it is, and stamp it on every page in one pass.

The watermark is drawn on top of the existing page content, the way ink would sit on paper. The pages themselves don't change — text, images, layout stay exactly as they were. There's just an extra label visible through the page.

Where the stamp sits

Four positions cover the common shapes a watermark takes:

• Diagonal — large text rotated 30° across the middle of the page. The classic DRAFT or CONFIDENTIAL look. Visible without dominating, and hard to crop out of a screenshot.
• Center — same middle position but horizontal. Reads more like a stamp than a watermark; useful for short labels like "VOID" or "SAMPLE".
• Header — placed near the top, horizontal. Doesn't compete with body text in the middle of the page; works for status labels you want visible but tucked away.
• Footer — same idea, near the bottom. Common for copyright lines or internal-only markers.

The position you pick applies uniformly to every page. There's no per-page positioning — if you need different stamps on different pages, run the tool more than once with different page selections.

How loud the stamp is

Opacity controls how much the watermark shows. The default is 0.18 — visible enough to read at a glance but light enough that body text underneath is still legible. Push it up toward 0.4 if the watermark needs to dominate (legal documents marked VOID); pull it down toward 0.08 if it should be barely-there branding.

Font size defaults to 60pt for diagonal, which fits roughly 8–12 characters across an A4 page. For very short text (DRAFT, VOID) the default works; for longer phrases ("INTERNAL REVIEW ONLY") drop the size to 40 or 30 so it fits without clipping past the page edge.

Color defaults to neutral grey (#777777). Most use cases are best served by grey because it doesn't fight with whatever's on the page. Red is the standard for VOID/CANCELLED markings on official documents. Avoid pure black — it reads like body text and gets confused with content.

What you can stamp and what you can't

This is text-only watermarking. Type any string and it gets drawn on every page with the chosen size, color, opacity, and position. The font is Helvetica Bold throughout — the same universal stamp that "Page 5 of 20" uses, regardless of your document's language. Latin characters render predictably; non-Latin scripts (Arabic, Chinese, Cyrillic, Hindi) fall back to whatever Helvetica covers, which usually means missing or boxed glyphs. For non-Latin watermarks, a typical workaround is to use a transliterated Latin form — "DRAFT" instead of "ЧЕРНОВИК", "CONFIDENTIAL" instead of "機密".

There's no image-watermark mode in this flow. If you need a logo across every page, the closest path is to add it once to the document via edit-pdf on a page-by-page basis, or to use a vector logo as part of the document template before exporting to PDF.

What survives and what doesn't

• Original page content stays exactly as it was. Text, images, layout — untouched. The watermark is a new layer drawn on top.
• Bookmarks, annotations, links, form fields all survive. The tool draws over the page rather than rebuilding it from scratch.
• The watermark is baked in. It's not a separate object that can be toggled off in a viewer. To remove it later, you'd need to re-export from the original source — there's no undo from the watermarked PDF alone.
• Digital signatures are invalidated. Any modification breaks the signature binding. If the document is signed and the signature must remain valid, watermark a copy and keep the signed original separate.

If something looks off

• Watermark text is too long and clips off the edge. Drop the font size, or split a long phrase onto a single short word ("DRAFT" instead of "DRAFT — DO NOT DISTRIBUTE").
• Watermark is invisible. Opacity is too low or the color is too close to the page background. Try 0.2 opacity and grey on a white page; for dark-themed pages use a light color.
• Non-Latin characters render as boxes. The bundled font is Latin-only. Use a Latin transliteration or an English equivalent.
• The PDF is encrypted. Run it through unlock-pdf first; encrypted PDFs can't be modified.

Practical notes

1. Diagonal is the most forgery-resistant placement. A header or footer can be cropped out of a screenshot; a diagonal stamp across the middle has to be cloned out, which is much more work.
2. For documents that will be printed, bump opacity up to 0.25–0.3. Print darkens lighter colors less than screens do; what looks balanced on screen can disappear on paper.
3. For brand watermarks, keep opacity low (0.08–0.12) and use the brand color in muted form. The watermark is ambient identification, not a stamp.
4. The original file stays untouched. What you download is a new PDF with the watermark added; the source on your disk is unchanged.

What happens to your file

Watermarking runs in your browser. Open DevTools and watch the Network tab during the operation — there are no outbound requests carrying the file content. The PDF stays on your disk; the watermarked version is a new download alongside it.