You can go to the following folder to get the revision history:
C:\SProV8i SS6\ReadMe\HTML\STAAD.Pro
C: the drive where you have installed STAAD.Pro V8i SS6 SP2
C:\SProV8i SS6\ReadMe\HTML\STAAD.Pro
C: the drive where you have installed STAAD.Pro V8i SS6 SP2