Is it a hard and fast rule that an NPC can only have traits if they have the Additional Traits feat? Or is it more of a suggestion? I'm making my first NPC and would really like to know for sure.
If you're the GM then feel free to do whatever you'd like. Adding what is effectively a free feat can technically make them more powerful, but not enough to really unbalance them.
Ok, thanks.
I created an Upbringing feat in HeroLab called "Superior NPC" which grants the Additional Traits feat. So, justify it that way if you have a rule's lawyer player!