Simple calculation with round numbers:

- Pluto at 40 AU vs. Earth at 1 AU

- thus, Sun appears (1*1)/(40*40) = 1/1600 times as
bright from Pluto as from the Earth

- that corresponds to 2.5*log10(1/1600) = 8 magnitudes
fainter

- from Earth, the Sun's apparent magnitude is about -26

- so from Pluto, the Sun's apparent magnitude is about -18

For comparison, Venus appears roughly magnitude -4 as
seen from the Earth. Thus, Venus as seen from the Earth
is about 14 magnitudes fainter (= 400,000 times fainter)
than the Sun as seen from Pluto.

I leave it to you to do the comparison of apparent
angular sizes.

Michael Richmond