Altto
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Free · No sign-up · Runs in your browser

Add a watermark to a PDF.

Stamp a diagonal text watermark across every page — pick the wording and how strong it shows through, without a single page leaving your device. Password-protected PDFs need unlocking first.

Not uploaded — nobody sees it Choose text & opacity Applies to every page No subscription or account
Gray works well on most documents — pick your own if you'd rather match a brand color.

Several page jobs to do? Organise PDF lets you reorder, rotate, delete, split, merge and number pages on one screen.

Your file is never uploaded — it’s processed right here in this browser tab, on your device. It never reaches a server, so we never see it, copy it or keep it.

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At a glance

Watermark PDF: quick facts

Stamp a diagonal text watermark across every page of a PDF.

Updated

Price
Free. No sign-up, no watermark.
Text
Up to 60 characters, such as CONFIDENTIAL, DRAFT or your business name.
Style
Light, Medium or Dark opacity in any colour; it prints with the page.
Limits
Text only, on every page. Unlock password-protected PDFs first.
Privacy
Your file is processed in your browser and never uploaded.
How it works

How to add a watermark to a PDF

Type up to 60 characters, pick a colour and how strongly it shows, and the text is stamped once across every page at 45 degrees, sized to fit the page.

  1. 01

    Add your PDF

    Drop in the PDF you want to watermark.

  2. 02

    Set the text and opacity

    Type your watermark text and choose how strongly it shows.

  3. 03

    Save your PDF

    Get back the same document with the watermark on every page.

Tips

Tips for a watermark that does its job

A good watermark is easy to read, doesn’t get in the way, and says exactly what you mean.

  • Short words show up bestThe text is sized to fit across the page, so a single word like DRAFT comes out large while a long sentence comes out small. Keep it to a word or two, such as COPY or NOT FOR SALE.
  • Match the strength to the pageLight suits documents people need to read closely, Medium is a good starting point, and Dark stands out on photos and busy layouts, where a faint watermark gets lost.
  • Mark who each copy is forStamping a copy with who it went to, such as “Copy for J Smith, Sept 2026”, makes people think twice before passing it on, and shows where a leaked copy came from.
  • It deters, it doesn’t lockThe watermark is added as text on each page, so someone with PDF editing software could take it off. It’s a clear label and a deterrent, not protection, so only share the file with people you trust.

Like every Altto tool, this runs on your device — nothing you add is uploaded. How Altto works

45°

is the angle the text runs at, corner to corner across the page, so it can’t be cropped out without cutting into the document itself.

FAQ

Frequently asked questions

What the watermark tool can and can’t do. Need page numbers as well? Add them with Add Page Numbers.

What text can I use as the watermark?
Anything up to 60 characters — “CONFIDENTIAL”, “DRAFT”, a company name, or a date. It's stamped once, diagonally, across every page.
Can I make the watermark lighter or darker?
Yes — choose Light, Medium or Dark opacity, and pick any color you like from the color swatch. Gray at Medium opacity suits most documents; Light works well if the watermark shouldn't distract from dense text underneath.
Will the watermark cover up my content?
It's semi-transparent by design, so the text and images underneath stay fully readable through it — that's the point of a watermark rather than an opaque stamp.
Can I watermark a password-protected PDF?
Not directly — unlock it first with our Unlock PDF tool, then watermark it here.
Can I use a logo as the watermark?
Not at the moment, as the tool stamps text only. For most jobs a word works as well as a logo: your business name, CONFIDENTIAL or DRAFT in a colour that matches your branding reads clearly and keeps the file small.
Can I watermark only some pages?
The watermark goes on every page. To mark only some, separate those pages with Split PDF, watermark them here, then put the document back together in order with Merge PDF.
Will the watermark show when printed?
Yes. It’s part of each page, so it prints along with everything else, at the strength you chose. On a black-and-white printer a coloured watermark prints as grey, so print a test page if the look matters.
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PDF to Black and WhiteTurn a colour PDF into greyscale or pure black and white.