Is there a way to use Winbatch to decrypt or encrypt files with PGP keys?
WinBatch doesn't contain support of PGP encryption. However if you have a tool installed that handles PGP encryption, you can automate it via commandline or COM automation (if supported).
Or if you have a newer version of WinBatch that supports dotNet, you could use something like:
OpenPGP encrypt in .NET: http://www.didisoft.com/net-openpgp/ and http://www.didisoft.com/net-openpgp/examples/encrypt-file/