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.

Not uploaded — nobody sees it Choose text & opacity Applies to every page No subscription or account

Drop your PDF here, or click to browse One PDF file · the watermark is stamped onto every page

Watermark text

Color

Gray works well on most documents — pick your own if you'd rather match a brand color.

Opacity

Your file is never uploaded — it’s processed right here in this browser tab, on your device. There’s no server involved, so we never see it, copy it or keep it.

How it works

Three steps, no waiting on a server

Altto's watermark tool works right in your browser tab, so there's no upload queue and no “processing your file” spinner tied to someone else's servers.

Add your PDF

Drop in the PDF you want to watermark.

Set the text and opacity

Type your watermark text and choose how strongly it shows.

Save your PDF

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

Why this runs in your browser, not on a server

A document worth watermarking — a draft, a confidential contract — is exactly the kind you wouldn’t want sitting on a stranger’s server first. Altto skips that step completely — there’s no server for it to go to.

Nothing is uploaded, everEvery PDF is handled by code that runs in this browser tab, because there’s no server on the other end. That also means we can’t see it, copy it or keep it.
No account, no email wallWatermark as many PDFs as you like without signing up or handing over an email address.
Applied consistently everywhereThe same text, size and opacity are stamped onto every page, so nothing gets missed.

documents stored on our servers. There’s no server involved at all — the watermarked PDF is built once, then everything happens locally.

FAQ

Frequently asked questions

The practical details on what this tool can and can’t do. Need to number the pages too? See 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.

Is my PDF uploaded anywhere?

No — nothing is ever uploaded. The file is loaded and stamped entirely inside this browser tab. There's no server involved at all, so there's nothing for Altto to see, copy or keep.

Can I watermark a password-protected PDF?

Not directly — unlock it first with our Unlock PDF tool, then watermark it here.

Do you keep a copy of my document?

No. There's no upload, so there's nothing on our side to keep. See the Privacy Policy for details.

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