Can you reverse pump down a heat pumps system?

Yes the same way you pump down a a/c, shut off unit at stat, remove electronics housing compartment door, place gages on service ports and close the liquid side service valve using your service wrench , then almost shut the suction side . keep it about a half of turn open. press in contactor and monitor gages till almost all pressure is gone then quickly close valve the rest of the way. newer unit have a low pressure switch in them making this difficult with out leaving ref in system as they cut out at around 50 psi. barring this you must recover ref into bottles