AlteredIdea: Just Another Thought
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PDF Watermark

Add a custom text watermark to every page of your PDF.

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Preview

CONFIDENTIAL

How to add a watermark to a PDF online for free

AlteredIdea's PDF Watermark tool lets you stamp any text: "CONFIDENTIAL", "DRAFT", your company name, or any custom string: onto every page of your PDF. You can control the position (diagonal, center, top, or bottom), font size, opacity, and color to match your branding or document needs.

The watermark is embedded directly into each page's content stream using pdf-lib, not added as a separate annotation layer. This means the watermark persists in print, in PDF readers, and when the document is viewed on any platform. All processing happens in your browser: no files are sent to a server, and there are no upload limits or account requirements.

How to watermark a PDF: step by step

  1. 1
    Upload your PDF
    Drop the PDF onto the upload zone. The file stays in your browser throughout.
  2. 2
    Type your watermark text
    Enter the text to display: e.g. 'CONFIDENTIAL', 'DRAFT', or your company name.
  3. 3
    Customize appearance
    Adjust color using the color picker, set font size with the slider, and control transparency with the opacity slider.
  4. 4
    Choose position
    Select Diagonal, Center, Top, or Bottom. A live preview updates as you change settings.
  5. 5
    Click Add Watermark and download
    The watermarked PDF is generated locally and downloaded automatically.

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Frequently Asked Questions

How do I add a watermark to a PDF for free?
Upload your PDF to AlteredIdea PDF Watermark, type your watermark text, choose position and styling, then click Add Watermark. The watermarked PDF downloads immediately.
Can I place the watermark diagonally?
Yes. The 'Diagonal' position option rotates the watermark text 45 degrees across each page: the most common watermark style.
Is the watermark permanent?
Yes. The text is drawn directly onto each page in the PDF using pdf-lib, so it cannot be removed by simply viewing the file.
Can I set the watermark transparency?
Yes. The Opacity slider goes from 5% to 100%, so you can create subtle background watermarks or bold, opaque stamps.
Are my files uploaded to a server?
No. All watermarking is done locally in your browser. Your files never leave your device.
Can I choose a custom watermark color?
Yes. Use the color picker to choose any color for your watermark text. The tool also includes a live preview.
Does the watermark cover all pages?
Yes. The watermark is applied to every page in the PDF.
Can I remove a watermark added by this tool?
Watermarks added by AlteredIdea are embedded into the page content and cannot be trivially removed with basic tools.
What font is used for the watermark?
The watermark uses Helvetica Bold, a standard PDF font that is universally available without embedding.
Can I watermark a scanned PDF?
Yes. The watermark text is drawn on top of every page regardless of whether the content is scanned or digital text.

AlteredIdea vs alternatives

vs Smallpdf / ILovePDF: Those services upload your files to their servers. AlteredIdea processes everything in your browser: your files never leave your device.

vs Adobe Acrobat online: Adobe requires an account and has file size limits on the free tier. AlteredIdea is unlimited and account-free.

vs desktop software: No installation, no licence fees, no OS dependency. Works on any device with a browser.

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