How is this different from other online PDF tools?

Most online PDF tools send your files to a remote server for processing. This tool processes everything locally in your browser using client-side JavaScript. Your files are never transmitted to any server, which means your document content stays entirely under your control.

Are my PDF files uploaded?

No. Your files are read directly by your browser. Your files are never transmitted over the network. The tool works entirely within the browser tab you have open.

Can I verify that files are not uploaded?

Yes. Open your browser's developer tools (F12), go to the Network tab, and watch for any outgoing requests while using the tool. You will see no file data leave your browser. The site may record an anonymous page-view count, which never includes your files and can be disabled.

Does this tool work offline?

Yes, once the page has loaded the tool processes your files entirely in your browser; tool functionality needs no network connection. You can disconnect from the internet and continue using it.

What happens when I refresh the page?

Because nothing is stored on a server, refreshing the page clears your current session. Any files you had selected will need to be selected again.

Does this tool store my files?

No. Files are held in browser memory only for as long as the page is open. Closing or refreshing the page discards them. Nothing is written to disk by the tool, and nothing is sent to a server.

Can this tool unlock password-protected PDFs?

No. This tool does not attempt to remove or bypass PDF password protection. If you know the password, the Unlock PDF tool on this site can remove it locally; then this tool can process the file.

What technologies does this tool use?

This tool uses client-side JavaScript and pdf-lib for local PDF structure editing.

Does this tool use WebAssembly?

No. This tool uses client-side JavaScript and pdf-lib for local PDF structure editing. No WebAssembly is involved.

How do I add a watermark to my PDF?

Pick a PDF from your device with the file picker, type your watermark text, then adjust the font size and opacity sliders to taste. Click apply and the watermarked file is prepared in your browser for you to save — nothing is sent anywhere.

Where does the watermark appear, and can I change its angle or color?

The text is drawn diagonally across the center of every page at a fixed 45-degree angle in gray, so there is no per-page or angle control in the current version. You can adjust the text, the font size (from 6 up to 300 points), and the opacity, which is set to about 30 percent by default so the text stays readable underneath.

Why do some characters in my watermark text come out wrong or cause an error?

The watermark is drawn using the standard Helvetica font, which covers basic Latin letters, digits, and common punctuation. Accented letters, emoji, or non-Latin scripts such as Chinese or Arabic may not render and can cause the operation to fail, so it is best to stick to plain Latin text.

Does the Add Watermark to PDF tool cost anything to use?

Adding a text watermark to your PDF is completely free — no account, no sign-up, and no limit on how many documents you watermark — and it always will be. Every step, from entering your watermark text and adjusting the opacity or rotation angle to downloading the finished file, runs entirely inside your browser using pdf-lib, so your document is never sent to a server or anyone else's infrastructure.

Add a Text Watermark to PDF Privately — Your Document Stays on Your Device

Select a PDF, enter your watermark text, adjust the style, and download the watermarked file — all processing is local with no upload.

Quick answer

What it does: Select a PDF, enter your watermark text, adjust the style, and download the watermarked file — all processing is local with no upload.
Free?: Yes — 100% free, no account or sign-up.
Files uploaded?: No — everything is processed in your browser.
Works offline?: Yes — once the page has loaded.
Best for: Marking draft contracts or NDAs with DRAFT or CONFIDENTIAL before sharing for review.
Good to know: Watermarks are added as drawn text elements; they are not password-protection and can be removed by editing the PDF structure.

How it works

Select a PDF file from your device using the file picker.
The file is read into browser memory using the FileReader API — no data leaves your browser.
Enter the watermark text and adjust options such as font size, opacity, and rotation angle.
pdf-lib draws the watermark text onto each page using its built-in drawing primitives.
The watermarked PDF is offered as a download directly from your browser.

When to use this tool

Marking draft contracts or NDAs with DRAFT or CONFIDENTIAL before sharing for review.
Adding a company name or copyright notice to a PDF before distributing it publicly.
Stamping SAMPLE across proposal pages sent to prospects before final sign-off.
Note: watermarks are drawn text elements, not password protection — they can be removed by editing the PDF structure.

Frequently asked questions

How is this different from other online PDF tools?: Most online PDF tools send your files to a remote server for processing. This tool processes everything locally in your browser using client-side JavaScript. Your files are never transmitted to any server, which means your document content stays entirely under your control.
Are my PDF files uploaded?: No. Your files are read directly by your browser. Your files are never transmitted over the network. The tool works entirely within the browser tab you have open.
Can I verify that files are not uploaded?: Yes. Open your browser's developer tools (F12), go to the Network tab, and watch for any outgoing requests while using the tool. You will see no file data leave your browser. The site may record an anonymous page-view count, which never includes your files and can be disabled.
Does this tool work offline?: Yes, once the page has loaded the tool processes your files entirely in your browser; tool functionality needs no network connection. You can disconnect from the internet and continue using it.
What happens when I refresh the page?: Because nothing is stored on a server, refreshing the page clears your current session. Any files you had selected will need to be selected again.
Does this tool store my files?: No. Files are held in browser memory only for as long as the page is open. Closing or refreshing the page discards them. Nothing is written to disk by the tool, and nothing is sent to a server.
Can this tool unlock password-protected PDFs?: No. This tool does not attempt to remove or bypass PDF password protection. If you know the password, the Unlock PDF tool on this site can remove it locally; then this tool can process the file.
What technologies does this tool use?: This tool uses client-side JavaScript and pdf-lib for local PDF structure editing.
Does this tool use WebAssembly?: No. This tool uses client-side JavaScript and pdf-lib for local PDF structure editing. No WebAssembly is involved.
How do I add a watermark to my PDF?: Pick a PDF from your device with the file picker, type your watermark text, then adjust the font size and opacity sliders to taste. Click apply and the watermarked file is prepared in your browser for you to save — nothing is sent anywhere.
Where does the watermark appear, and can I change its angle or color?: The text is drawn diagonally across the center of every page at a fixed 45-degree angle in gray, so there is no per-page or angle control in the current version. You can adjust the text, the font size (from 6 up to 300 points), and the opacity, which is set to about 30 percent by default so the text stays readable underneath.
Why do some characters in my watermark text come out wrong or cause an error?: The watermark is drawn using the standard Helvetica font, which covers basic Latin letters, digits, and common punctuation. Accented letters, emoji, or non-Latin scripts such as Chinese or Arabic may not render and can cause the operation to fail, so it is best to stick to plain Latin text.
Does the Add Watermark to PDF tool cost anything to use?: Adding a text watermark to your PDF is completely free — no account, no sign-up, and no limit on how many documents you watermark — and it always will be. Every step, from entering your watermark text and adjusting the opacity or rotation angle to downloading the finished file, runs entirely inside your browser using pdf-lib, so your document is never sent to a server or anyone else's infrastructure.