How to embed signature, which provided by third party service #178

[ntqp97]

There is a service in my country which provides a digital signature, When creating a signature, the signer is authenticated using the private key associated with an X.509 certificate, as issued by third party service.

I convert the PDF I want to sign to base64
I authenticate using my phone number and my password
the service returns the signature and also a X.509 certificate and digest
I need to sign the PDF myself
Is there any way I can complete step 4 with your library?