In essence a PKI certificate is a way to protect your public keys in your digital signature or digital certificate. These certificates are used as a way to validate public cryptographic keys when the time comes for the public keys to be renewed. The PKI certificate is typically issued by the same Certificate Authority that issues your digital certificate and allows you to merge your digital signature with a public key and where necessary a personal identifier such as your real name.
It is very important for you to make sure that the certificate authority you are planning to use is a legal provider for the PKI Certificate you are planning to use. You can verify this by looking them up on the PKI Certificate Revocation List before you spend any money. You will find that Digi-Sign is fully authorized to issue PKI certificates and that we have never been on revocation list.