I'd like to be able to decrypt a PGP file into a text file using the command line. I realize there's the PGP Command line utility which is probably the best solution, but is there anyway to achieve this with pgp desktop? Possibly using ppgwde?

yes you can decrypt

HOW TO: Decrypt a Partition using the pgpwde Command-line Utility

I read through it but i only see options to decrypt entire partitions. I want t decrypt a single file someone sent me, using a private key and passphrase i was provided with. I'd like to have it output to a file.

No, PGP Desktop does not include a command line tool that can decrypt PGP files.

Does the Symantec (PGP) Encryption Desktop 10.3 version come with a .dll  I can reference in C# code for a custom service that will encrypt/decrypt individual files?

thanks.

Symantec PGP products use the PGP SDK for encryption.  Depending on your use case, you may be permitted to utilize the PGP SDK:

https://www-secure.symantec.com/connect/downloads/symantec-pgp-software-development-kit-sdk

If your use case falls outside what is permitted, you will need to get a different license from Symantec.  In that case, I can put you in contact with the Product Manager for the PGP SDK.

There is no C# interface to the PGP SDK.

Regards,