We have created an iOS app for a client, which we would like them to code-sign and distribute.
What is the best method for this? If I Build and Archive, then Share a
Check out Erica Sudan's App Signer. This utility allows an unsigned IPA to be resigned with a different provisioning profile.
Easy to use, so perfect for your needs.
http://ericasadun.com/ftp/Macintosh/
Obviously this all depends on them having an iOS Developer contract and having created their own provisioning profile