PDFLosslessRuns in your browser

Add Watermark to PDF

Stamp text across every page — diagonal, centred or tiled. The conversion is lossless — every pixel, sample or byte in the source is preserved.

Not uploaded to any serverConverted on this deviceGone when you close the tabHow this works

Drop your files here

PDF · up to 200 MB each

or paste files from your clipboard

Ready when you are

Stamp text across every page — diagonal, centred or tiled. Everything happens in this tab; nothing is sent anywhere.

⌘K to search converters

How to use it

1
Add your files
Add Watermark to PDF works with PDF. Drop them in, browse for them, or paste from your clipboard.
2
Choose your options
Tune watermark text, position and opacity — or leave the defaults, which are sensible.
3
Run it and download
Press the button and save the result. Everything happens on your device, and nothing is uploaded.

Privacy, in plain words

Is it safe? Your PDF is not uploaded anywhere

What “uploaded” normally means. On most online converters, pressing the button copies your file across the internet onto a computer owned by that website. That copy is what the word “upload” means, and it is the part nobody explains.

What happens instead. This site does not do it. There is no server here that receives files, so your PDF is read, converted and handed back by the browser you are using right now. It never travels — so there is no copy to store, read, leak or hand over.

Check it yourself in ten seconds

Turn off your Wi-Fi after this page has loaded, then convert a file anyway. It still works, because everything needed is already on your device.

The longer explanation of how this works, and the full detail of what is and is not stored on the privacy page.

Why this matters more than it sounds

PDF is the format people use for exactly the documents they would not hand to a stranger. It matters more than it sounds, because of what PDFs usually are:

Bank statements

account numbers, balances, every payee you have

Signed contracts

your signature, and terms you may be under NDA about

Tax returns

income, dependants, tax file or social security numbers

Passport and visa scans

the single most useful document for identity theft

A file that is never sent cannot be kept, leaked, subpoenaed or used to train anything. That is a property of how this works, not a promise about how carefully it is run.

How Add Watermark to PDF works

Stamp text across every page — diagonal, centred or tiled. Everything happens inside this page: the file is read from your device into memory, processed there, and handed back as a download. It is never sent anywhere, and closing the tab discards it.

What it accepts: PDF. Files are identified by their contents rather than their name, so a mislabelled file is still handled correctly.
What you get back: A PDF file, downloaded straight to your device.
What happens to the data: Nothing is re-encoded. The content that comes out is identical to the content that went in, byte for byte, and running it twice changes nothing.
Size limit: Up to 200 MB per file. Because the work happens on your own machine, available memory is the real constraint — a laptop handles far more than a phone.

The settings, and what each one changes

Add Watermark to PDF exposes 7 settings. The defaults are chosen to suit the common case, so changing nothing is a reasonable way to start.

Text: Free text, used exactly as you type it.
Position: Choose between Diagonal across page, Centre, Bottom, Top and others.
Opacity: Takes 3 to 80 %. Applied to every file in the batch.
Text size: Takes 10 to 140 pt. Applied to every file in the batch.
Colour: Choose between Grey, Red, Blue, Black.
Page range: Comma-separated. Use a trailing dash for 'to the end'. The page editor above fills this in as you work.
Per-page turns: Set by the page editor when you turn individual pages. Page number, then the angle.

Worth knowing before you start

The watermark is drawn as a normal page object. It is a visual mark, not a security control: anyone with a PDF editor can remove it.

Measured, not estimated

What this tool actually does to a file

Stamping the word CONFIDENTIAL across all six pages.

On every sample measured, the result came out larger — 7% larger at best and 1.3× larger at worst.

Each row is one document, chosen because this tool behaves differently depending on what is inside the file.
Sample	In	Out	Change
A text reportSix pages of text and nothing else — the case where there is very little for a compressor to find.	6.7 KB	8.4 KB	+26%
Text with figuresText pages carrying two embedded images — the ordinary shape of a report, and the one most PDFs in the world actually have.	24.5 KB	26.3 KB	+7%

Produced by this site's own converter. The same code that runs in your browser, at the same default settings, so these are the bytes you would download.

Samples are generated from a fixed seed rather than taken from real photographs or documents, so the corpus is reproducible and carries no licensing question — and so the numbers predict the shape of your result rather than its exact size. Measured 2026-10-01. The method, and the command that regenerates every figure on this page, are on the how it works page.

About these formats

Accepts

Portable Document Format

Fixed-layout documents that look identical everywhere.

Extensions: .pdf
MIME type: application/pdf
Best for: Sharing documents · Printing · Contracts and forms
Compatibility: Universal.

The watermark is drawn as a normal page object. It is a visual mark, not a security control: anyone with a PDF editor can remove it.

Good to know

Add Watermark to PDF — questions

How does Add Watermark to PDF work?

Stamp text across every page — diagonal, centred or tiled. Add your files above, adjust anything you want to change, and press the button. The result downloads straight to your device.

Is there anything I should watch out for?

The watermark is drawn as a normal page object. It is a visual mark, not a security control: anyone with a PDF editor can remove it.

Is Add Watermark to PDF safe — are my files uploaded to a server?

No, nothing is uploaded. On most online tools, pressing the button copies your file across the internet onto a computer owned by that website, where it is processed and then sent back. That copy is what "upload" means. This tool does not do it: your file is read and processed by the browser you are using right now, stays on this device the whole time, and is discarded when you close the tab. Turn off your Wi-Fi after the page loads and it still works, which is the quickest way to confirm it.

Can I use this on confidential or personal documents?

Yes — that is the case it was built for. Because the file never leaves your device, a confidential document is no more exposed than it is sitting in your own folder: there is no transfer, no copy on anybody else's hardware, no retention period and no staff with access. Nothing about the file is logged either — not its name, not its size, not its contents.