Digital signature
Seal a PDF with your certificate (.pfx), checked by Acrobat. Nothing is uploaded: the work happens on this device.
About Digital signature
Seals a PDF with your certificate, a .pfx or .p12 file, so a reader such as Acrobat can show who signed and that nothing has changed since. Shown as a box on the last page, or invisible in the reader’s signature panel. The certificate and its password stay on your device and are forgotten when you leave.
How to use it
- Add the PDF you want to sign.
- Tap Choose your certificate and pick your .pfx or .p12 file.
- Type the certificate’s password.
- Leave Show the signature on the page ticked for a visible box, choose the first or last page, and add a reason and a place if you like.
- Press Sign it digitally and save the signed PDF.
Good to know
A digital signature is worked out from the document’s exact contents with a key only the certificate holder has. A reader such as Acrobat then shows who signed, which authority issued their certificate, and whether anything has changed since. The visible box carries your name and the date; switch it off and the signature still sits in the reader’s signature panel.
Finish the document before signing. Any later change to the file, even adding a page number, shows as a change after signing. A locked PDF must be unlocked first with Remove a password. A signature someone else added earlier stays valid when you add yours, because yours is appended rather than rewritten.
An expired certificate is refused, with the date it ran out, because readers would mark the signature as not valid. Whether a reader also shows your identity as trusted depends on whether it trusts the authority that issued the certificate, not on this tool.
Questions people ask
Can I use my DSC on a USB token?
No. A web page cannot reach a token. Use the signing utility that came with it. See digital signature with a DSC.
Why was my certificate refused?
It may have expired: the tool shows the date rather than make a signature readers would mark invalid.
Can I sign a locked PDF?
Remove its password with Remove a password first.
Is my certificate uploaded?
No. The file and its password are read in your browser, used once, and forgotten when you leave the page.