Is it possible to add a subject alternative name when converting PEM certificate to DER format.
openssl x509 -outform der -in Certificate.pem -out Certificate.der -extensions SAN -subject-alternative-name 'alternative name'
If possible, so how to make this operation with openssl?
No, of course not, this would change the certificate and invalidate the signature. You're asking the exact same thing as "I have a certificate for a domain I own, chedy.com, and I want to add google.com to the Subject Alt Names list, what is the openssl command for that?".
The difference between DER and PEM is just a base64 encoding.
You need to generate a new certificate with the SAN you want.
