Below is the description for "Aid Another" in http://paizo.com/pathfinderRPG/prd/coreRulebook/combat.html
Question here: is this action also treated as an "attack" because it said "roll an attack roll" or it only ends up with +2 bonus to AC or +2 bonus on next attack?
I guess the answer is the latter, because it said "distracting or interfering" with an opponent but not "attack". But I have to persuade GM who insist "aid another" is also an attack which would cause melee damage..
In melee combat, you can help a friend attack or defend by distracting or interfering with an opponent. If you're in position to make a melee attack on an opponent that is engaging a friend in melee combat, you can attempt to aid your friend as a standard action. You make an attack roll against AC 10. If you succeed, your friend gains either a +2 bonus on his next attack roll against that opponent or a +2 bonus to AC against that opponent's next attack (your choice), as long as that attack comes before the beginning of your next turn. Multiple characters can aid the same friend, and similar bonuses stack."