PGP Encryption and signing There is a requirement for me to both encrypt a file with the clients public key provided to us and sign the same file with our (my own) private key which they have the corresponding public key for.

Should this be a 2 step process (i.e. first encrypt then sign) Or can this be done in one shot using a single PGP command with multiple parameter? If so, can you please provide a sample of what the command would look like?
Should this be a 2 step process ...


Yes, you need to do it in 2 steps with common algorithms such as RSA, ECDSA, ECIES, etc. (because they're not signcrypt algorithms). 

You should first encrypt, then sign, as this ensures with (slightly) better confidence that signature don't reveal information about the file/message. 


  If so, can you please provide a sample of what the command would look like?


Programming questions are off-topic. But if you really don't know how to use the command line, there is a high chance you can hurt yourself doing it, so a GUI app is recommended.