Just to add to Desertdweller's post, the porter did stay with the car for the entire journey, and I have read that a Pullman conductor was required whenever two or more Pullmans were in a train. If there was only one Pullman in the train it might be assigned to a Porter In Charge, who, for additional pay, took on the duties of a conductor. From the passenger's point of view, the difference between the train conductor and the Pullman conductor was that the railroad conductor worked in his assigned crew district and was replaced a crew-change points by another conductor, while the Pullman conductor remained with the train for the entire journey. Thus the passenger might encounter a succession of train conductors on a long trip (although as a Pullman passenger he hardly had occasion to have contact with the train conductor once his rail ticket had been collected), but he would see the same Pullman conductor the whole time. As mentioned above, the Pullman conductor was responsible for the Pullman Company's revenue, represented by the Pullman ticket, and if there was a duplicate sale or any other reservation mixup it was up to the Pullman conductor to deal with it. As mentioned, he had nothing to do with the operation of the train except as it affected the Pullman cars in his charge.
Trivia question: anybody know what Pullman car line operated over the greatest number of railroads from origin to destination?