The JFK PDC will usually contain the SID (standard instrument departure and various climb profiles as well) if the PDC has to be modified while the aircraft is taxiing, because of a runway change for example... then the controller may speak a little more slowly as they know that the the person taxying the aircraft has to listen out and monitor the new clearance and the person copying the clearance still has to have some spare capacity to monitor the taxi...
...something like that!
k-o-t-s