It definitely gets higher when you leave Low Earth Orbit, because you're leaving the Earth's magnetic field; so the ISS is definitely at the low end of the scale of Voyager's exposure.
Not sure how it varies as you leave the solar system - depends on the exact balance between Solar Energetic Particles (particle radiation from the sun) and Cosmic Rays (particle radiation from outside the solar system), and on how much the cosmic radiation increases as Voyager leaves the heliosphere.
Not sure how it varies as you leave the solar system - depends on the exact balance between Solar Energetic Particles (particle radiation from the sun) and Cosmic Rays (particle radiation from outside the solar system), and on how much the cosmic radiation increases as Voyager leaves the heliosphere.