Add Watermark to PDF

A watermark is a deterrent, not a lock

Be clear-eyed about what this does. The word you type is added to each page as ordinary page content, in the same way a heading or a caption is. It is not a security feature, it is not encryption, and it is not redaction.

Anyone with a proper PDF editor can select that text and delete it in a few seconds. It is also real, selectable text, so a reader can drag over the middle of the page and copy the word "DRAFT" straight out. That is not a flaw so much as the nature of the format: PDF has no layer that content can hide in.

What a watermark does achieve is making casual reuse obvious and awkward. Someone who screenshots a page or forwards a file cannot pretend they did not see "NOT FOR DISTRIBUTION" across it, and a printed copy carries the mark permanently. That is genuinely useful for drafts, quotes, sample chapters, proofs and internal circulation. If your goal is to stop a document being opened at all, you need password encryption from a desktop application instead.

One more honest note: the mark is painted over the existing content rather than beneath it. Opacity, not layering, is what keeps your text readable underneath.

Centre or tiled, and how the spacing is worked out

Centre puts one stamp in the middle of each page, rotated 45 degrees if you chose diagonal. It is the cleanest look, and the least intrusive when the opacity is low.

Tiled repeats the same stamp on a grid. The grid is not fixed: the horizontal step is your text's measured width plus 40 points, with a floor of 180 points, and the vertical step is three times your font size, with a floor of 120 points. Longer words and larger type therefore spread further apart automatically, instead of overlapping into mush.

A concrete case: "CONFIDENTIAL" at 48 points measures roughly 375 points wide, giving a horizontal step near 415 points and a vertical step of 144. On an A4 page, 595 by 842 points, that produces about two columns and six or seven rows, so somewhere around a dozen stamps per page.

Tiled is the better choice when you expect someone to crop or screenshot part of a page, because there is no clean area to lift. It is the worse choice for anything that will be read carefully, since even a faint repeating pattern behind dense body text tires the eye.

Picking settings that survive printing

Opacity defaults to 25 percent, which reads clearly on a screen without fighting the text. Printing changes the calculation. Home inkjets and office lasers tend to render light greys lighter than the screen suggests, and a 5 or 10 percent grey mark can disappear almost entirely on paper. If the printed copy is what matters, try 30 to 40 percent and print one page as a test.

Colour affects the same judgement. Grey is the least intrusive and disappears on a photocopy, which some people want and others do not. Red reads as a warning and stays visible after a black and white photocopy as a mid-grey. Blue sits between the two, and suits marks like a company name or "SAMPLE" that are informational rather than a caution.

On size: 48 points is roughly 17 mm tall and spans a good part of an A4 page diagonally. Below about 24 points a centred mark stops reading as a watermark and starts looking like a stray line of text. Above 90 points the ends of a long word will run past the page edges and simply be clipped.

Limits worth knowing

Only one line of text is supported, up to 60 characters, and there is no image or logo option. The text is set in the standard Helvetica font, which covers Western European characters, so Chinese, Japanese, Korean, Arabic, Hebrew, Thai and emoji will not render. Latin letters with accents are fine.

The mark goes on every page. There is no way to exclude a cover or apply it to a range. There is also no position control beyond centre and tiled, so a small corner mark is not available.

The preview draws sheet one with browser text as an approximation, and shows it in a bold weight, while the exported file uses regular Helvetica. Treat the preview as a guide to placement and density rather than a proof, and check the downloaded file before sending it.

Password-protected documents are refused on opening. Everything runs in your browser, so your files never leave your device.

Where it fits in a workflow

Watermarking is best done last, after the document is otherwise final, because a mark added before you merge or trim pages will still be there on pages you later wanted clean. If you also need footer numbering, Add Page Numbers to PDF stacks on top of a watermarked file without disturbing it. For a document that needs a signature rather than a status stamp, use Sign PDF. Marking a page does not change its size much, but if the file was already large, Compress PDF is the next step.

Questions

Can someone remove the watermark I added?

Yes, with a desktop PDF editor. It is drawn as normal page content and can be selected and deleted. Treat it as a visible marker of intent, not as protection.

Will it cover my text and make the document unreadable?

At the default 25 percent it sits over the page but stays translucent enough to read through. Lower it to around 15 percent for dense text, or choose centre rather than tiled.

Can I use my logo instead of a word?

No, this page only stamps a single line of text. A logo needs a desktop editor that can place an image on every page.

Does the file get bigger?

Barely. A short string of text and one embedded standard font add a few kilobytes in total, whether the document has 3 pages or 300.

Can I watermark only some pages?

Not here. A workaround is to split out the pages you want marked, stamp them, and merge the document back together.