The barycenter of Pluto and Charon is in space between the two bodies, close to Pluto. It is the center point of the animation below. The image is roughly to scale. Note that the two bodies are mutually tidally locked, with the same sides always facing each other.
Charon is 17,536 km from the system barycenter, and 19571 km from the center of Pluto. Its surface gravity is 0.288 m/s2. It has a mean radius of 606 km.
Pluto has a surface gravity of 0.62 m/s2 and a mean radius of 1,187 km. The atmosphere of Pluto, though very thin, is also an issue over time. At the surface it is 1 Pa, 0.001% the pressure of Earth's atmosphere (right now, while it is close to the sun). Above the bottom layer of the atmosphere, its scale height is estimated at 50 to 60 km.
Would it be difficult to put an orbiter in a stable orbit around Pluto? Or around Charon? What kind of station-keeping might be involved?