If a signature is not validated in a PDF, we see Validity unknown with a question mark. You need to validate the signature to make it valid.

Thunderbird 142 release is here with message linking, PDF signatures, Fastmail calendar fixes, and some new-found respect for ...

If you receive a PDF or other digital file that requires your signature, you can easily do so using your phone. Whether you use an iPhone or an Android phone, both include built-in options for ...