Digital Signature PDF
This digital signature PDF tool signs files with your own certificate, so readers can see who signed and whether anything changed afterwards. The certificate never leaves your device.
How to digital signature PDF
Drop your PDF into the box.
Choose your .p12 or .pfx certificate file and type its password.
Add a reason, location or contact if you want.
Sign and download the PDF.
Digitally sign a PDF with a certificate
This is a cryptographic signature (PKCS#7, SHA-256), not a picture of your name. It needs your own certificate file in .p12 or .pfx format with an RSA key, plus its password. Readers such as Acrobat then show who signed and flag the file if anything changed after signing.
For a drawn or typed signature on the page, use Sign PDF instead.
Limits to know before you sign
There is no trusted timestamp, so the signing time comes from your device. Signatures already in the file are not preserved, so sign last. Whether a reader shows the signer as trusted depends on who issued your certificate. To check the result, run Validate PDF Signature. The guide to digitally signing a PDF explains certificates in more detail.
Guides
Frequently asked questions
How do I add a digital signature to a PDF?
Drop the PDF here, choose your .p12 or .pfx certificate, enter its password and sign. Download the signed PDF.
What is the difference from Sign PDF?
Sign PDF places a visual signature on the page. This tool adds a certificate-based signature that shows who signed and whether the file changed.
Do I need a certificate to digitally sign a PDF?
Yes. You need your own .p12 or .pfx certificate file with an RSA key and its password.
Is my certificate uploaded?
No. The certificate and its password stay on your device.
Does it add a trusted timestamp?
No. There is no timestamp from a timestamp authority.
Can I add a second signature to an already signed PDF?
No. Existing signatures in the file are not preserved, so signing again replaces them.
How do I check the signature?
Open the file in a reader such as Acrobat, or use Validate PDF Signature.