Add watermark

How to watermark a PDF

A watermark is there to be read by somebody who is not reading carefully. It stops a draft being quoted as final, it reminds whoever has printed a copy that the copy is not theirs to pass on, and it survives being photographed off a screen.

1. Drop the PDF on the box at the top.
2. Type the word. Short words work: one long sentence across a page is unreadable both as a watermark and as a page.
3. Choose how it sits. Across the page, corner to corner, is the one everybody recognises.
4. Set the size, the colour and how strong it is, and watch the page beside the controls.
5. Press Save the PDF.

How strong to make it

The setting nobody gets right first time. Faint enough and the page still reads normally but the mark is easy to miss in a printout. Strong enough to be unmissable and the words underneath become hard work.

Around a fifth of full strength is the usual answer for something people have to read. Push it up for a page whose whole job is to say DO NOT USE.

Repeated all over is the layout to choose when the mark is there to stop a page being cropped and reused as a clean one. A single diagonal word can be cut off; a grid of them cannot.

What a watermark does not do

It does not protect the document. The word is drawn on the page like anything else on it, and anybody with a PDF editor - including this one - can take it off again. It marks a document; it does not lock one.

It is also not a password. This site does not put passwords on PDFs at all, and if the file must not be opened by the wrong person, a watermark is not the tool for that.

What it does do is make a careless mistake unlikely, which is what it is for. Somebody about to send a draft to a client will notice DRAFT across it.

Letters it can write

Western letters, numbers and punctuation, accents included. Other alphabets - Arabic, Chinese, Greek, Cyrillic - cannot be written with the fonts built into a PDF, and embedding a whole font for a one-word stamp would add a megabyte to every file. The tool says so rather than writing a row of blank boxes.