depends how badly pitted---you can usually get away with having them turned
Your brake pads may need to be replaced, or your rotors may be "Pitted" and may need to be "Turned"
When Brake Rotors Are To Thin To Turn On A Brake Lathe To Have The Minumn Thickness. They Need To Be Replaced.
No just the bad one.
They need replaced when they wear out.
Your brake rotors are warped and need replaced/resurfaced.
When they are warped or worn beyond legal limits.
Your rotors are warped. You need new brake pads and the rotors turned at a machine shop or replaced.
If you are wondering whether it is possible to replace one's own brake rotors or not because you drive an older vehicle that need brake rotors replaced, then the answer is no.
Most of the time, you can get by with just replacing the pads. The rotors generally do not need to be turned if there is no pedal pulsation or vibration. Rotors will need to be replaced if the exceed the minimum thickness which is stamped on the web (area with lug holes).
Warped rotors. They need to be removed, turned or replaced.
Could be that the rotors are "out of round" and need either to be resurfaced or replaced
Rotors may be out of "round" (lateral runout) and need to be resurfaced or replaced