Stamp CONFIDENTIAL or DRAFT Across Every PDF Page
Add a diagonal text watermark to a document as real vector type, not a flattened image.
About the PDF Watermark Tool
Type the wording you need — the field starts on CONFIDENTIAL, and DRAFT or the recipient's name are equally common — and it is drawn once across the centre of every page in the document. Four controls shape it: font size in points from 12 to 120, opacity from 5 to 100 percent starting at a subtle 22, a colour picker defaulting to red, and a toggle for the classic forty-five degree diagonal.
Unlike marking an image, the text here is added as genuine vector type inside the PDF. It stays crisp at any zoom and adds almost nothing to the file size, because a string and a font reference cost far less than a repainted page. That also means the mark is a real object in the document rather than baked into the pixels, so someone determined and equipped could remove it — this is a clear signal of status, not a security control. The stamping runs in your browser.
Key Features
- Vector text, not pixels: The mark is drawn as type, so it stays sharp at any magnification and barely affects file size.
- Diagonal or horizontal: The forty-five degree angle is on by default, with a toggle for a straight horizontal mark instead.
- Opacity from 5 to 100: Start subtle at the default so the document stays readable, or push it up for something unmissable.
- Any colour: The picker starts on red, the convention for status marks, but any shade can be used to suit a house style.
- Applied to every page: The watermark lands on all pages in one pass, so nothing in a long document is missed.
How to Use the PDF Watermark Tool
- Add the PDF you want to mark.
- Type the wording — CONFIDENTIAL, DRAFT, or a recipient's name.
- Set the size, opacity and colour, and choose diagonal or horizontal.
- Apply the watermark and download the marked copy.
How It Works
pdf-lib embeds the standard Helvetica Bold face and draws the string once per page, measuring the text width to centre it and adjusting the placement geometry when the diagonal rotation is applied. Because it uses one of the fonts built into the PDF specification, no font file is embedded and the file grows by almost nothing. That choice carries one real constraint: the standard fonts cover the Western European character set, so wording containing Cyrillic, Greek, Chinese, Japanese or Korean characters cannot be encoded and will fail. There is also no page range — the mark goes on every page — and only a single centred instance is drawn per page rather than a repeating tile.
When You Need It
A medical writer circulates a draft study protocol to investigators for comment, and the one thing that must not happen is a working version being mistaken for the approved document once it has been forwarded a few times. A diagonal DRAFT across every page makes the status unmistakable at a glance in print or on screen. The protocol describes an unpublished trial design, so uploading it to a watermarking site to mark it confidential would be a contradiction in terms. Firms issuing priced proposals and teams releasing pre-decision papers mark documents the same way.