I used to have a Papillon (well two), so I know a lot about them. Right now I have a Pomeranian though. I never remember Gizmo (my pap) trying to pick things up off the floor, the younger you train them and keep them busy, the better behaved they are. Papillons never really jump after the initial greet, my pap was so well-mannered and intelligent for his small size.
He never had any health problems with his knees at all, always perfectly happy since birth. You need a great breeder though that does testing, etc. Gizmo actually had grandparents that were show dog/agility champions.