Hover is a specific maneuver of the Fly skill that requires a DC 15 skill check. "You generally need only make a Fly check when you are attempting a complex maneuver. Without making a check, a flying creature can remain flying at the end of its turn so long as it moves a distance greater than half its speed." Also, "Action: None. A Fly check doesn't require an action; it is made as part of another action or as a reaction to a situation."
Hover is necessary to make a full-attack while flying, since otherwise a flying character must move "a distance greater than half its speed." However, a DC 15 is not hard to make for the most part.