Take it to an alignment shop. It could be just adjustment or the trailing arm could be bent.

Agree as above. If possible find an aligner who uses equipment that 'floats' all four wheels at once. If only the fronts are on turn-tables and the rears on a solid (not movable) platform when adjustments are made it may be only the suspension rubbers twisting to give the new alinement numbers. If the who car is 'floating' then the numbers are true as the car body cannot resist the adjustment forces.