How to convert a certificate file in DER (Distinguished Encoding Rules) format to PEM (Privacy Enhanced Mail) format? I know that PEM file format uses printable characters only and is safe to be included emails.

If you want to convert a certificate from DER format to PEM format, you can use the Microsoft "certutil -encode input_file output_file" command as shown in this tutorial:

C:\fyicenter>\windows\system32\certutil -encode FYIcenter.crt FYIcenter.pem
Input Length = 530
Output Length = 788
CertUtil: -encode command completed successfully.

C:\fyicenter>type FYIcenter.pem
-----BEGIN CERTIFICATE-----
MIICDjCCAXegAwIBAgIQs/MzYEEeK4BFzXXPlYiiPTANBgkqhkiG9w0BAQQFADAc
MRowGAYDVQQDExFGWUljZW50ZXIgUm9vdCBDQTAeFw0xMjEyMTIxOTM0MDlaFw0z
OTEyMzEyMzU5NTlaMBwxGjAYBgNVBAMTEUZZSWNlbnRlciBSb290IENBMIGfMA0G
CSqGSIb3DQEBAQUAA4GNADCBiQKBgQCa+tWJJB0izeU/HjCohMtHXGXHjnOHMLhq
YtTVOS4ZnxVjFZWi7AozmTkqSDYBmv1j3ggo0uVqh/sTtX/s+0OkPPgwFlpKdyxJ
W9yo4E3tvBzYKcbjhTPNoPUL2N45vKyzNfDSClHqFWfuuwS+bPOHybzXzKurxAh0
...
-----END CERTIFICATE-----

⇒ Microsoft "certutil -encode..." - Converte PEM file to DER

⇐ Microsoft "certutil -encode" Command Options

⇑ Other Microsoft "certutil" Commands

⇑⇑ Microsoft "certutil" - Certificate Management Tool