After trying out several demo versions, I settled on this one. For $19, it does a thorough job stripping out all the metadata, and you can use Batch mode to clean a group of files quickly.
BatchPurifier -
http://digitalconfidence.com/BatchPurifier.html
HINT: Use the demo version of MetadataTouch, which has a few more features but it's more expensive. Once you verify that it will do what you need, buy the cheaper BatchPurifier. It uses the same tech, but with a few less options it's cheaper to use and simpler.