The correct method is to remove the trim from both the inside and outside, cut the nails used to install the door on the top and latch side(leaving the nails untouched on the hinge side), and move the top to get a uniform gap along the top. Then move the latch side to get the same uniform gap along the side of the door. Using finish screws(available at most hardware stores) helps eliminate the movement while nailing. The best way to pull the nails from the trim is to pull out the back---that does not mess up the surface. Then replace the trim.