Yes you need to implement at project level based on your requirement using workflow or other means.
Thnaks for your reply! That's very helpful. But it raises the question - if it isn't a requirement that it be a workflow, is it possible in CQ 5.4 to add Tags (or other metadata not embedded in files) to DAM assets in a batch using the OOB CQ GUI? I am not seeing it mentioned anywhere in the documentation. (Or the GUI.)
Excellent. I didn't realize batch tagging was possible via asset share.