What a watermark is actually for
A watermark tells whoever opens a document how to treat it: that it is a draft, that it is confidential, that it belongs to you. That is a real and useful job. What it cannot do is enforce any of those things, and people reach for it expecting that it will. This page separates the two, and covers the choices that decide whether the mark helps or gets in the way.
Which tool you need
Marking a document as a draft, a copy or confidential
Watermark PDF with a word across the pages. This is what the tool is for and what a watermark genuinely achieves.
Actually stopping people opening or printing it
Password protect PDF. A password is the only thing here that decides who can open a document; a mark on the page is a label, and labels do not lock.
Your own logo rather than a word
Choose a PNG or a JPG. What the file actually contains decides whether it can be used, not what it is named, and a photo carrying a camera turn is refused rather than placed the wrong way up.
Something on the page rather than across it
Edit PDF places text, a picture or a drawing exactly where you want it on one page. A watermark is for the same mark repeated across a document.
A mark on some pages and not others
Every page is selected when the document opens. Deselect the ones to leave alone — the cover, the appendix — and only the rest are marked.
Page numbers rather than a mark
Add page numbers is the tool for that, with positions, starting numbers and a Page 1 of 10 form a watermark cannot produce.
Behind the words, or over them
By default the mark goes in front of the page's own content at 25% opacity, so the words stay readable through it and the mark shows even on a scanned page, whose own picture would hide anything placed behind it.
A mark in front covers content without removing it. What is underneath is still in the file and still selectable, so a mark in front is a visual statement rather than a way of obscuring anything — the same thing that is true of a box drawn over a page in Edit PDF.
Why a tiny repeated mark is refused
Halving the size of a repeated mark quadruples the number of copies on the page, and that is the number that grows without limit rather than the mark itself. Past a ceiling the tool refuses instead of writing a file no reader could open.
The fix is any of three things: make the mark larger, widen the spacing, or place it once in the middle. A large diagonal word across the page is also what a reader recognizes as a watermark, so the limit tends to push in a good direction.
Repeating a picture does not make the file much bigger either way. One copy of it is stored for the whole document however many times it appears, so what grows is the instruction to draw it again.
What to know before you start
- A watermark can be removed by anyone who can open the document, with the same kind of tool that added it.
- Words are written in Latin or Devanagari script from a bundled font, and a word using characters outside those is refused rather than written as empty boxes.
- Nothing is uploaded. The pages are measured and the mark written in your browser, on this device.