PBInitialize is provided as a diagnostic and as a performance enhancement. It is normally called implicitly the first time you call any of the API functions and as such does not need to be called explicitly. It does, however, return success or failure and so might be useful if you are having problems. It also, obviously, does some initialization which, while extremely fast, may not be fast enough for some critical uses so for this reason as well it was decided to provide PBInitialize publicly so that it can be called explicitly at some initialization time that may not be so performance critical.
PBInitialize Provided for manual initialization under special circumstances.
PBGetLibVersion These two are provided as diagnostic aids.
PBSetUnhandledExceptionFilter Allows special processing of unhandled exceptions which occur while using library resources.