Sign with certificate
Sign a PDF with your own certificate file so Adobe Acrobat shows who signed it and whether it was changed afterwards. Your certificate and password stay on this device.
Drop a PDF here
or click to browse
PDF files only. Processed in your browser.
How to use Sign with certificate
- 1Choose your PDF. Do any editing, filling or compressing first: the signature must be the last change.
- 2Choose your certificate file (.pfx or .p12), type its password and press Open certificate. You see who it is for, who issued it and when it expires.
- 3Pick Stamp on the page (drag the box where you want it) or Invisible. Add a reason and place if you like.
- 4Press Sign the PDF and download the signed file. Open it in Adobe Acrobat to see the signature.
Questions
Is this different from the Sign PDF tool?
Yes. Sign PDF puts a picture of your handwriting on the page. This tool adds a digital signature: a cryptographic seal made with your certificate. Readers such as Adobe Acrobat show who signed and warn if even one byte of the file changes afterwards. You can use both: add the handwriting first, then seal the file.
Are my certificate and password safe?
They are used only inside this page, on your device, to make the signature. Nothing is uploaded, nothing is stored, and the password is cleared as soon as the certificate is open. Closing or reloading the page forgets everything.
Why does Acrobat say “signer unknown” or “validity unknown”?
A certificate you made yourself is not on Acrobat’s list of trusted authorities, so it cannot vouch for who you are. The signature still works: it shows whether the file was changed after signing. A certificate from a certificate authority is trusted when the reader trusts that authority.
Can I use my USB token (DSC) or Aadhaar eSign?
No. A USB token never lets its private key leave the token, so a web page cannot use it, and Aadhaar eSign needs an online service. Use the token’s own software for those. This tool works with a certificate saved as a .pfx or .p12 file.
Which certificates work?
RSA certificates (the common kind) in a .pfx or .p12 file, new or old style, with or without a chain of authorities. Elliptic-curve (ECDSA) certificates are not supported yet, and a certificate that has expired or is not valid yet is refused.
Is there a trusted timestamp?
No. A trusted timestamp needs a timestamp server on the internet, which would send data out of your device. The signing time comes from your device’s clock.
Why is a PDF that is already signed refused?
Adding a second signature this way means saving the file again, which would break the first signature. Sign the original once, or remove the old signature first.
Is my file uploaded anywhere?
No. The file is opened and changed inside your browser, on your own device. There is no upload step and no server that receives it. You can even switch off your internet after the page has loaded and most tools keep working.