From the Advanced Class Guide Playtest 2:
Effortless Aid (Ex): The investigator can perform aid
another actions as a move action instead of a standard
action. An investigator can expend one use of inspiration
to instead perform an aid another action as a swift action.
Spending inspiration in this way is a free action.
Does this mean that an Investigator with this talent can perform multiple Aid Another actions in the same round? RAW, it seems like you could perform one as a move action, and another as a standard action. Or you could perform three aid another actions by spending inspiration.
Yes, he can do three. The question really is, "can all three boost the same thing and stack?" being able to go multiple aid's isn't new, there's the feat swift aid that lets anyone do it as a swift and standard. I think that yes they can all stack for one big boost. but remember, it only last for 1 check, and only for the 1 target.