Sign PDF in Firefox — Browser-Based Tool

Sign any PDF document directly in Mozilla Firefox without installing add-ons, extensions, or desktop software. SigPDF runs entirely in your browser — draw or type your signature, place it on your PDF, and download the signed file in seconds.

No add-ons neededPrivacy-first browserNo file uploadsFrom €2.08/month

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Why Sign PDFs in Firefox with SigPDF?

Firefox is the browser of choice for privacy-conscious users worldwide. Built by the non-profit Mozilla Foundation, Firefox has a long history of putting user privacy first — with features like Enhanced Tracking Protection, strict cookie policies, and transparent open-source development. SigPDF shares this privacy-first philosophy.

Firefox includes pdf.js, a built-in PDF viewer that can display documents and fill basic form fields. However, pdf.js does not support adding signatures to PDFs. To sign a document, Firefox users previously had to install an add-on, download a desktop application, or upload their PDF to a cloud-based service. SigPDF eliminates all of that — it runs directly in your Firefox tab with no installation required.

Firefox Add-ons vs SigPDF

While Firefox's add-on ecosystem includes PDF tools, using add-ons for document signing has drawbacks:

  • Privacy risks — Many add-ons require permissions to access your browsing data or upload files to external servers for processing.
  • Maintenance burden — Add-ons need to be updated, and incompatible updates can break functionality after Firefox releases.
  • Performance impact — Each add-on consumes memory and can affect Firefox's performance.
  • Trust issues — Add-on ownership can change, potentially introducing unwanted behavior.

SigPDF avoids all of these issues. It is a standard web page you visit when you need it. Your PDF is processed entirely within Firefox using client-side JavaScript. No data leaves your device.

Privacy That Matches Firefox's Values

If you use Firefox, you likely care about privacy. SigPDF respects that. Your PDF is loaded into Firefox's memory, processed with client-side JavaScript, and the signed document is generated locally on your device. No file is ever uploaded to SigPDF's servers or any third party. This client-side architecture also means SigPDF works even when your internet connection is slow or intermittent — once the page loads, the signing tool operates entirely offline.

How to Sign a PDF in Firefox with SigPDF

  1. Open Firefox and navigate to SigPDF
  2. Click “Choose File” or drag and drop your PDF into the editor
  3. Create your signature — draw with your mouse or touchpad, type your name, or upload a signature image
  4. Click on the PDF page to place your signature where needed
  5. Download the signed PDF — your signature is permanently embedded in the file

Frequently Asked Questions

Can I sign a PDF in Firefox without installing an add-on?
Yes. SigPDF is a web application that runs entirely in Firefox without any add-ons, plugins, or downloads. Open SigPDF in Firefox, upload your PDF, draw or type your signature, and download the signed document. No installation required.
Does Firefox have a built-in PDF signing feature?
Firefox has a built-in PDF viewer (pdf.js) that can display PDFs and fill basic form fields, but it does not include a signature tool. SigPDF fills this gap by providing a complete PDF signing experience directly in your Firefox browser.
Is my PDF private when I sign it in Firefox with SigPDF?
Yes. SigPDF processes your PDF entirely within Firefox using client-side JavaScript. Your file never leaves your device — there are no server uploads, no cloud storage, and no third-party access. This aligns well with Firefox's privacy-focused philosophy.
Does SigPDF work on Firefox for all platforms?
Yes. SigPDF works in Firefox on Windows, macOS, Linux, and Android. Whether you are using Firefox on a desktop, laptop, or mobile device, SigPDF provides the same signing experience without any platform-specific requirements.
Why choose SigPDF over Firefox add-ons for PDF signing?
Firefox add-ons for PDF signing may request broad permissions, upload your documents to external servers, or introduce security risks. SigPDF requires no installation, processes everything locally in your browser, and provides complete privacy. There is nothing to manage, update, or worry about.
Can I sign multi-page PDFs in Firefox?
Yes. SigPDF handles multi-page PDFs seamlessly in Firefox. You can scroll through all pages of your document, zoom in to read fine print, and place signatures, initials, dates, and text fields on any page. All processing happens locally using client-side JavaScript.
How much does SigPDF cost to use in Firefox?
SigPDF costs from €2.08/month billed annually, with unlimited document signatures. There are no per-document fees, no watermarks, and no envelope limits. Sign one document a month or a hundred — the price stays the same.

Related Resources

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