Does the type of weapon used (piercing, slashing, bludgeoning) have any effect in Pathfinder RPG? For example, in AD&D 2e, the type of weapon modifies attack rolls according to the defender's armor type. (E.g., piercing weapons have an attack bonus on chain mail and so on…) Does something like this exist in Pathfinder too?
Yes. There are consequences for the weapon type used, but modifiers against armour types have been discarded.
DR: Some monsters are resistant to certain types of damage. This can be seen in DR for skeletons where their DR is 5/Bludgeoning.
Feats: Some feats also require certain weapon types to be effective, for example Bleeding Critical requires a slashing or piercing weapon to be used.
Smashing: Smashing objects requires a blungeoning or slashing weapon.