pdf tool
Add a watermark to a PDF
Type the watermark text, such as DRAFT or CONFIDENTIAL, choose diagonal or horizontal, the size, colour and opacity, and it is stamped in the centre of every page or just the pages you name. A live preview shows the first page before you save.
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- Runs on your device, nothing is uploaded
- Free, no sign in
- No watermark, no file limit
How it works
- 1
Open the PDF
Choose the file or drop it on the box. The first page is drawn with DRAFT across it, and a signed file is flagged straight away.
- 2
Write the watermark
Replace DRAFT with your own text. Characters the standard fonts cannot draw are named under the box, and the save button waits until they are gone.
- 3
Style it
Choose Diagonal or Horizontal, then set the size, opacity, colour and font. The preview redraws as you move each control.
- 4
Pick the pages and save
Leave Pages empty for every page, or type a range such as 2 to 5, 8; the preview moves to the first page in the range. Press Add the watermark and save.
How the watermark is drawn
The text is written into each page's content as real vector text, centred on the visible area of the page, at the opacity you set. Diagonal runs from the lower left corner towards the upper right at the page's own angle, so it is steeper on a portrait page than on a landscape one. Pages stored with a rotation are handled, so the watermark reads the right way up on screen whatever the file says internally. Because it is text rather than a picture, it stays sharp at any zoom and adds only a few hundred bytes per page.
Choosing text, size and opacity
Short words work best: DRAFT, COPY, SAMPLE, CONFIDENTIAL or a name. At 72 pt a word of six or seven capitals crosses most of an A4 page diagonally; longer phrases need a smaller size, and the preview shows if the text runs off the page. An opacity of 15 to 30 percent keeps the page readable while making the mark obvious, and a mid grey or a muted red prints well on office printers. Very low opacity can vanish on a cheap printer, so test one page on paper first. Courier Bold gives every letter the same width, which suits reference numbers, and Times Bold reads as more formal on legal documents.
Why plain ASCII only
Every PDF reader has fourteen standard fonts built in, and using one of them means nothing has to be embedded in the file. The catch is that these fonts cover a limited character set, so this tool keeps to plain letters, digits and punctuation and refuses anything else with a message naming the character, rather than drawing a gap or a box. The PDF is read and rewritten in your browser; nothing is uploaded and nothing is stored, ever.
Watermark first, sign afterwards
A watermark changes the bytes of the file, and a digital signature covers those bytes exactly, so watermarking a signed PDF makes the signature report the document as altered. Always watermark the unsigned copy and sign last. OneCraft e-signature certification locks the completed PDF, so it cannot be edited or annotated afterwards without breaking the signature, which is the point: the signed version is final.
Limits worth knowing
A text watermark is a visible label, not protection: anyone with a PDF editor can delete it, because it sits in the page content as ordinary text. It may also be found by copy and paste or search. Encrypted files are refused with a message, since pdf-lib cannot write them. Images, logos and tiled patterns are not offered. Pages left out of the range are copied across unchanged.
Limits
- Text watermark only, no image or logo.
- Standard PDF fonts only, Helvetica, Times or Courier in bold, so the text must be plain ASCII; accented letters and other scripts are refused with a message.
- Watermarking rewrites the file, so a digitally signed PDF will report the document as changed, and the tool warns you before you save one.
What it does not do
- It does not remove an existing watermark.
- It does not tile the text across the page or place it in a corner; it is centred on each page.
- It does not upload the file or protect it with a password.
Questions people ask
Can someone remove a watermark from a PDF?
Yes, with a PDF editor and a little effort, because the watermark is ordinary text in the page content. It deters casual copying and labels a document clearly, but it is not security. For a document that must not be altered, a certified digital signature or a flattened image of each page does more than any visible mark.
Will the watermark show when the PDF is printed?
Yes. It is drawn into the page content, not added as a screen only annotation, so it prints exactly as it appears in the preview. Light colours at low opacity can fade on some office printers, so print a test page. If it looks too faint, raise the opacity to 30 or 40 percent or choose a darker grey.
Can I watermark only the first page or skip the cover?
Yes. Type the pages into the Pages box, such as 1 for the first page only or 2- for every page after the cover. Ranges and single pages can be mixed, such as 2 to 5, 8. Leave the box empty to stamp every page. The preview switches to the first page in your range.
Why is my watermark text with an accent refused?
The tool draws with the standard fonts every PDF reader has built in, and it keeps to plain ASCII so the text renders the same everywhere. A letter such as é or ü is named in the message under the text box. Replace it with the plain letter, or use a PDF editor that can embed a full font if the accent matters.
Does adding a watermark make the PDF larger?
Hardly. The text is drawn with a standard font that every reader already has, so no font file is embedded, and each page gains only a short instruction to draw the words. A ten page file grows by a few kilobytes at most. Large jumps in size come from images, which this tool never adds.
Sign the final version after watermarking
Take what you made here into e-signatures.
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Background reading: the question page on this.
Built with pdf-lib (MIT), pdf.js (Apache-2.0).
Written and checked by the OneCraft team. Last checked .