Free Online PDF Watermark Tool - Protect Your Documents

Add Watermark to PDF

Protect your documents by stamping custom text diagonally across every page.

or drag and drop a PDF here

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This text will be applied diagonally as a semi-transparent stamp on all pages.

How to Add a Watermark to a PDF Securely

Whether you are sharing a sensitive business proposal, distributing a rough draft to a client, or sending out proprietary research, you want to ensure your intellectual property is protected. Adding a watermark to your PDF is one of the most effective ways to establish ownership, prevent unauthorized distribution, and indicate the status of a document (such as "CONFIDENTIAL" or "DRAFT").

Our Free Online PDF Watermark Tool allows you to instantly apply a professional, semi-transparent text stamp diagonally across every page of your document. Best of all, it happens securely right in your web browser.

Why Use Our Watermark Tool?

Protecting your documents shouldn't require downloading heavy desktop software or paying for premium subscriptions. With our web-based utility, you can:

  • Maintain 100% Privacy: Unlike cloud-based tools that upload your sensitive documents to remote servers, our tool uses modern browser technology to process your PDF locally. Your files never leave your computer.
  • Save Time: The watermark is automatically applied to every single page in your document simultaneously, saving you from having to stamp pages manually.
  • Enjoy Free Access: There are no hidden fees, daily usage limits, or annoying promotional watermarks (we only add the text *you* type!).

Frequently Asked Questions (FAQ)

Will the watermark cover up my text?
No. To ensure your document remains fully readable, our tool applies the watermark using a semi-transparent gray color (40% opacity). It is dark enough to be clearly visible and deter copying, but light enough so the underlying text and images can still be easily read.
Can the watermark be removed by someone else?
The watermark is deeply embedded into the PDF’s content stream. While no digital watermark is 100% invincible against professional PDF editing software, our method acts as a strong, permanent visual deterrent against casual copying, printing, and screenshotting.
How does the tool place the watermark?
Our algorithm automatically calculates the dimensions of each individual page in your PDF. It then centers your custom text, sizes it appropriately, and applies a 45-degree diagonal rotation for that classic, professional watermark appearance.
Does this work on mobile devices?
Yes! Since the tool relies entirely on your device's web browser, you can easily watermark documents directly from your iPhone, iPad, or Android device without installing any apps.