Distance continues to grow between Pam and Jim, both literally and figuratively, until they both amicably decide to separate. Jim stays in Philly and Pam stays in Scranton.
The documentary shows that neither of them are doing well in their respective situations. Jim is depressed and alone, tired of his new bachelor life. Pam hates Scranton. Her mom helps with the kids, but it just isn't right being at Dunder Mifflin.
So it all comes down to the last episode. Having had enough, they both quit their jobs without notice. Pam drives home, grabs the girls, and heads toward Philly. Jim walks out of Athlead, heading to Scranton. They just want to be together, no matter where.
Pam's SUV is low on gas. She pulls into the gas station, where oddly enough Jim proposed years before. She recognizes the place as tears well up in her eyes. She turns off the car and waits. Waits for Jim. He doesn't come.
She sighs, gets out, fills up, and gets back in the car. She pulls away and is stopped by another car trying to get to the pump. Of course it's Jim.
We return to the same wide shot in which Jim proposed. They talk feverishly, but we don't hear. They hug and kiss. Jim gets in the drivers seat of the SUV, leans between the seats and kisses his girls. Pam gets in the passenger seat.
They drive off, leaving his car and their past behind.