I know that most actors in the game are levelled, and that their skill levels then depend on the player's level. What I'm wondering is when do the actors update their values from being level 1 little pansy men to being fully powered enemies when a high level player approaches them. Is it OnLoad? OnCellAttach? Anyone know?
Also, is there a formula for how many skill ranks an NPC gains per level?

Actors only have their skills raised to the correct level when they are first loaded in the game. So if you met Lydia when you were still level 8, and now you are level 50, you will find that bandits beat the **** out of her.

Maybe the skill levels get updated in an OnReset event. Not sure, since I haven't tried it. I do know that changing race will update an actor's skill levels though.

http://www.creationkit.com/Class

Disabling then Enabling the Actor also resets their level/stats, but if they are a follower they cannot be in the players service when trying to reset them.

TargetNPC.SetPlayerTeammate(False)TargetNPC.EnableAI(False)TargetNPC.Disable()Utility.Wait(0.1)TargetNPC.Enable()TargetNPC.SetPlayerTeammate(True, True)TargetNPC.EnableAI()

Also note if the Actor has some follower only equipment (or any equipment) it will also be 'Reset'.