AFTER STARTING THE AIRCRAFT ENGINE FOR INTENDED FLIGHT, THE PILOT INADVERTENTLY DROPPED HIS FLIGHT CHARTS AND CHECKLIST TO FLOOR OF THE AIRCRAFT. THE PILOT REACHED DOWN TO PICK THEM UP AND FAILED TO NOTICE THAT HIS AIRCRAFT WAS ROLLING FORWARD. HE SAID THAT WHEN HE BECAME AWARE OF THE SITUATION, HE IMPROPERLY APPLIED THE BRAKES AND ADVANCED THE THROTTLE INSTEAD OF RETARDING IT. BEFORE CORRECTIVE ACTION COULD BE TAKEN, THE AIRCRAFT STRUCK A PARKED AIRCRAFT.