How to add a watermark to a PDF
Last updated: 2026-07-28
You are circulating a proposal that is not final, or sending a specification to a vendor who should not forward it around. The convention is a pale diagonal word across each page: DRAFT, CONFIDENTIAL, COPY. Easy enough if you still have the source document — less so when all you have is the PDF someone emailed you.
Adding the watermark
Open your PDF in StickPDF and click Watermark in the document tools row. The dialog asks for the text (a single line), opacity from 5% to 60% defaulting to 18%, an angle from −90° to +90° in 5° steps defaulting to −30°, and a colour: near-black, navy, or red. Apply, and the mark lands on every page at once, centred, sized to 75% of the page width. Click 'Download PDF' for a new merged file; the original is untouched, and nothing leaves your browser.
Opacity: 18% is not an arbitrary default
Eighteen percent is the level at which a reader notices the word immediately but never has to fight it to read the paragraph underneath. It is tempting to push the slider higher, but past roughly 35% the watermark starts competing with body text — tolerable on a title page, harmful on a page dense with figures, where a stroke crossing a column of numbers turns a 6 into an 8. Below about 10% the opposite happens: a mark that reads clearly on screen can vanish on a black-and-white laser printer. For paper, sit between 15% and 25% and test one page.
Short words beat sentences
The text is scaled to fill 75% of the page width, so the width is fixed and the letter size is whatever fits. Add characters and every character shrinks proportionally. CONFIDENTIAL spans the page as an unmissable band; "This document may not be reproduced without written permission" renders as a thin grey smear nobody reads and still sits on top of your text. Put the full notice in a footer instead. A watermark answers one question — what is the status of this document? — in a word or two.
Why the angle matters
The −30° default earns its place. A horizontal watermark disappears the moment somebody crops the top and bottom of a page or screenshots just the text block; a diagonal one runs corner to corner, so almost any crop takes part of a stroke with it and announces that the page has been altered. It reads better, too: body text runs horizontally, so a horizontal mark shadows the letterforms, while an angled one cuts across them and the eye separates the layers. Between 20° and 45° works well.
DRAFT and CONFIDENTIAL do different jobs
A status mark — DRAFT, FOR REVIEW — is a courtesy to your reader, meant to stop a working version being mistaken for the final one and forwarded to a client. It should be obvious at a glance but easy to read past, since someone is going to read the document carefully. Navy or near-black at 15–20% suits it, and keep an unmarked master, because you will need to reissue without it.
A confidentiality mark addresses the recipient's obligations rather than their convenience. It should be harder to ignore, which is why red is conventional, and can carry a little more weight — up to around 25%. Even here readability wins: an over-marked page just gets screenshotted section by section.
What a watermark does not do
A visual watermark deters casual reuse. It does not protect a document. Anyone holding the file can screenshot it, retype the contents, or paint the mark out in an image editor. It does not encrypt anything, restrict who can open the file, or track where it goes, and it confers no legal protection. What it does achieve is still worth having: it keeps reminding a reader that the document belongs to someone else, and makes its status unambiguous if the file turns up where it should not.
How the text is rendered
StickPDF draws the watermark onto a canvas and embeds it as a transparent PNG rather than as PDF text, at 3× resolution so the edges stay crisp in print. Any script renders exactly as it looks on screen, with no font embedding failures. The trade-off: in the exported PDF the watermark is not selectable and not searchable, and screen readers will not announce it. For a watermark that is usually fine — even useful, since copying a paragraph will not splice CONFIDENTIAL into it.
Adjusting or removing it
Each watermark behaves like any other placed element: click to select, drag to move, resize with the corner handle, delete with the Delete key — the same handling as any image you place, covered in how to add an image to a PDF. One rough edge: there is currently no single button to remove all watermarks. You delete them page by page, so treat the watermark as the last step before download, and to change the wording or colour, reopen the original PDF and apply it fresh.