OK, the PC is jumping from the plane, untrained, with what might be a parachute, and what might be someone's hiking pack, and trying to land on a building and not the fence.
Sooooo....
How high up is the plane?
What are the winds?
How far above the roof is he?
OK, we'll say it's all safe to do.
Now, Knowledge (Popular Culture) since parachuting would be covered somewhat, with a -4 to get into his rigging. If he puts it together wrong, he'll crush his testicles, fall out of the rig, or dislocate something.
Jump Check: To get far enough away from this little crop duster without slamming his head into the landing gear.
Now, sometimes you use a static line (PAF! Out and open!), or a hand-held drag-open (Throw and POOF! Open!), or a release (Count to whatever, pull the ring, and pray)
I'd give him a gimmee on this.
Now, do a tumble check to land. Believe me, landing with a chute is NOT like jumping off of a first story building. The shock from the hit can be a lot worse. You jump off of the back of a moving truck for landing practice, but it's still not the same. If you blow this landing, you'd get a Reflex check to change the damage from regular to subdual damage.
Then, if the winds aren't too bad, get out of your rig before the chute drags you off the building. Reflex save.
You can plug in the DC's youself.
I, personally, just added Paradrop (Which let me add Airborne Feat, Jumpmaster Feat) skill to the skill list, and included it as an option in a few of the starting occupations.
Sorry, but the "closed skill list" concept doesn't work for my game. Might work for yours, but not for mine.
Which is why I also added: "Knowledge (Extreme Sports)" to my game. Didn't bother my players, didn't bother me.
That's my $1.50, since 2 cents won't buy you jack nowdays.