I just got my warrior to rank 4 in warrior guild and got chance to train doubleattack. Will double attack cause I can hit with 2 weapons (one in each hand)per round or just 2 hits with same weapon in one hand?

It means you can use a second weapon in your "shield" hand BUT only weapons designated as second weapons (like some daggers) AND you only get to hit woth them IF you have a successful hit with your first weapon AND it depends on your skill in doubleattack/second weapon. What this really means is that you have restricted choice and you need to get that skill up, but if you can it can be really potent e.g. my level 100 Assassin with sword and doubleattacj skills at 12 could hit for around 50 with the Assassins dagger.