The average distance between Earth and Pluto is same as average distance of Pluto from the Sun. This is 0.000628 light years, nearly.
Explanation:
The average distance obetween two planets is nearly the average distance of the outer planet from the Sun. Earth is inner to Pluto. Average Sun-Pluto distance = 5906.4 million km. Divide by 149597870 to get distance in Au. Further divide by 62900 to get distance in ly.
