Originally posted on RealmSpire.com
During our game last Saturday, August 31st, there was some confusion on how Acrobatics worked when a character wanted to “tumble” to a position of better advantage. Using the latest version of the Core Rule Book (6th Edition – July 2013) on pages 87 and 88 these rules can be found as well as on d20PFSRD.com. I have been playing several systems lately and found that I was mixing a bit of D&D 3.5 with some D&D 4e and was mistaken in how I ruled that night.
A character can use Acrobatics to “tumble” around or through an enemy square. When moving around an enemy and passing through squares that an enemy threatens you need to succeed in a check against the enemy’s CMD to avoid being subject to an attack of opportunity. For example; If the enemy has a CMD of 20 you would need to roll a d20 and add your acrobatics number to your roll and get a 20 or better. When you roll an acrobatics check to do this you also ONLY need to make this roll one time in the turn – not for each threatened square you are moving through. Also note that the characters movement speed is halved. So if your movement is normally 30′ (6 squares) you would only be able to move 15′ (3 squares) when making an acrobatics check and you are considered to be flat footed so you would lose your DEX bonus to your AC. You can move at full speed by increasing the DC of the check by 10. So in the example above a roll of 30 or better would be needed to achieve this. When making an acrobatics check to move through an enemies square it would raise the DC of the roll by +5, so using the same example with an enemy that has a CMD of 20 you would need to roll a 25+ on your acrobatics roll or a roll of 35 to be able to do this while moving at full speed. In the case that there is more than one enemy that you are trying to avoid then the check goes up by +2 as you pass each one. If you have two enemies that both have the same 20 CMD then to pass the first one you would need to roll a 20+ to pass the first one and a 22+ to pass the second one or be subject to an attack of opportunity. If you fail the check, you lose the move action and provoke an attack of opportunity. If you take damage (from an opportunity attack) while using acrobatics you must make another check to avoid falling or being knocked prone.
via Dungeni.us http://dungeni.us/2013/09/08/acrobatics/