Re: HPAM 9.40 change log
Two pdf guides will explain the enhancements and defect fixes: ListOfFixes and ReleaseNotes. From a structure standpoint if you obtain 94 then under the Docs\Infos folder is a diff***.xml or you can use your own comparison tool that will identify the differences between the versions.
This will dictate extent of regression testing needed but overall how you are using the software, which modules, archiving, web, etc. will also help determine whether an upgrade is needed.