Add Watermark to PDF

Overlay a diagonal text watermark, like "CONFIDENTIAL" or "DRAFT", across every page of a PDF. Adjust the opacity and size, then download the watermarked file.

Click or drag & drop a PDF file

Supported: PDF files

Watermark Text

Opacity: 30%

Font Size: 48px

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Why use Add Watermark to PDF?

This tool overlays a diagonal text watermark across every page of a PDF using pdf-lib, entirely in your browser. Type the text you want to stamp, such as "CONFIDENTIAL" or "DRAFT", and the tool embeds a bold Helvetica font, measures its exact width, and centers it on each page before rotating it 45 degrees in gray. The opacity slider runs from 5% to 80% and the font size slider from 20px to 100px, so you can make the mark subtle enough to keep the page readable or bold enough to be impossible to miss, depending on the document. Because pdf-lib does the stamping locally, your file is never uploaded to a server. If the PDF cannot be opened, such as when it is password protected, you get a clear error asking you to remove the password first and try again. The finished file downloads automatically with "-watermarked" added to its original filename, ready to send on as a marked draft, proof, or confidential copy.

Key benefits

Adjustable opacity from 5% to 80% so the watermark does not obscure content
Adjustable font size from 20px to 100px
Applied automatically to every page in one pass
Rendered locally with pdf-lib, so your document never leaves your device
Free, no signup, and no extra branding added to the file

Features

Diagonal 45-degree text watermark rendered in a bold Helvetica font
Watermark text centered on each page using its measured width
Opacity slider from 5% to 80% in 5% steps
Font size slider from 20px to 100px
Downloaded file automatically named with a "-watermarked" suffix

Popular use cases

Marking a document as DRAFT or CONFIDENTIAL before sharing
Adding a company name across shared PDFs
Stamping sample or preview documents before sending drafts to clients
Labeling internal review copies before an external release

How to use Add Watermark to PDF

1
Upload a PDF
Click or drag a PDF file into the upload area.
2
Enter watermark text
Type the text you want overlaid, such as "CONFIDENTIAL" or "DRAFT". It defaults to CONFIDENTIAL.
3
Adjust opacity and size
Use the sliders to set opacity from 5% to 80% and font size from 20px to 100px.
4
Download the watermarked PDF
Click Add Watermark to stamp every page and download the result.

Frequently asked questions

Can I add an image or logo watermark instead of text?

This version supports text watermarks only. For a logo watermark, consider overlaying it with a PDF editor after adding your text watermark.

Will the watermark cover important content?

The watermark is placed at reduced opacity by default so the underlying content stays readable, adjust the opacity slider to your preference.

Is my file uploaded anywhere?

No. pdf-lib draws the watermark text onto each page inside your browser, so a draft or confidential document you are marking stays on your own machine.

What happens if I upload a password-protected PDF?

The file cannot be loaded, and you will see an error message asking you to remove the password before trying again.

Can I change the watermark color or angle?

Not in this version. The watermark is always gray and rotated 45 degrees; opacity, font size, and the text itself are the adjustable options.

Last reviewed: July 2026

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