Acrobatics measures your ability to perform tasks requiring coordination and grace. When you use the Escape basic action, you can use your Acrobatics modifier instead of your Unarmed Attack modifier.

Balance [one-action]

You move across a narrow surface or uneven ground, attempting an Acrobatics check against its Balance DC. You are Flat-Footed while on a narrow surface or uneven ground.

Critical Success You move up to your Speed.
Success You move up to your Speed, treating it as difficult Terrain (every 5 feet costs 10 feet of movement).
Failure You must remain stationary to keep your balance (wasting the action) or you fall. If you fall, your turn ends.
Critical Failure You fall and your turn ends.

Sample Balance Tasks
Untrained tangled roots, uneven cobblestones
Trained wooden beam
Expert deep, loose gravel
Master tightrope, smooth sheet of ice
Legendary razor’s edge, chunks of floor Falling in midair

Tumble Through [one-action]

You Stride up to your Speed. During this Movement, you can try to move through the space of one enemy. Attempt an Acrobatics check against the enemy’s Reflex DC as soon as you try to enter its space. You can Tumble Through using Climb, Fly, Swim, or another action instead of Stride in the appropriate environment.

Success You move through the enemy’s space, treating the squares in its space as difficult Terrain (every 5 feet costs 10 feet of movement). If you don’t have enough Speed to move all the way through its space, you get the same effect as a failure.
Failure Your Movement ends, and you trigger reactions as if you had moved out of the square you started in.

Acrobatics Trained Actions

Maneuver in Flight [one-action]

You try a difficult Maneuver while flying. Attempt an Acrobatics check. The GM determines what maneuvers are possible, but they rarely allow you to move farther than your fly Speed.

Success You succeed at the Maneuver.
Failure Your Maneuver fails. The GM chooses if you simply can’t move or if some other detrimental effect happens. The outcome should be appropriate for the Maneuver you attempted (for instance, being blown off course if you were trying to fly against a strong wind).
Critical Failure As failure, but the consequence is more dire.

Sample Maneuver in Flight Tasks
Trained steep ascent or descent
Expert fly against the wind, hover midair
Master reverse direction
Legendary fly through gale force winds

Squeeze

You contort yourself to Squeeze through a space so small you can barely fit through. This action is for exceptionally small spaces; many tight spaces are difficult Terrain that you can move through more quickly and without a check. 

Critical Success You Squeeze through the tight space in 1 minute per 10 feet of squeezing.
Success You Squeeze through in 1 minute per 5 feet.
Critical Failure You become stuck in the tight space. While you’re stuck, you can spend 1 minute attempting another Acrobatics check at the same DC. Any result on that check other than a critical failure causes you to become unstuck.

Sample Squeeze Tasks
Trained space barely fitting your shoulders
Master space barely fitting your head