You can restrict Jobs from working in certain regions by editing restrictedAreas.yml. You can additionally set a multiplier to reduce the amount of money received in a certain area. This is useful to setup if you want to prevent farming in MobArena or other types of mini-games.
restrictedareas: area1: world: 'world' multiplier: 0.0 point1: x: 125 y: 0 z: 125 point2: x: 150 y: 100 z: 150 area2: world: 'world_nether' multiplier: 0.0 point1: x: -100 y: 0 z: -100 point2: x: -150 y: 100 z: -150