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Digital Signature

Add a cryptographic digital signature to your PDF using X.509 certificates. Supports PKCS#12 (.pfx, .p12) and PEM formats. Your private key never leaves your browser.

Internet connection required

Signing may need to fetch certificate chain information from your certificate issuer's server to validate the signature.

Click to select a file or drag and drop

PDF Documents

Your files never leave your device.

About Digital Signature

Digital Signature signs the document with your X.509 certificate so recipients can verify who signed it and that it has not changed since.

How to use it

  1. Select your PDF, or drag it onto the drop area.
  2. Load your certificate file and enter its password.
  3. Choose the signature appearance, sign and download.

Your file stays on your device

This tool runs entirely in your browser. Your file is read from your device, processed in memory, and saved back to your device — it is never uploaded to QPDF or anyone else. Once this page has loaded, the tool also works with your internet connection switched off.

How QPDF keeps files private →

Good to know

  • Your certificate and its password are used only in your browser’s memory.
  • Recipients’ software will only show the signature as trusted if your certificate chains to an authority they trust.
  • Any later change to the signed PDF invalidates the signature, so sign last.

Related tools

All tools →
Validate Signature Check digital signatures and certificate details.
Sign PDF Draw, type or upload your signature and place it.