That is correct as would 400/500 (notice it adds up to 900) or any variant of above say 1200 /1500 12k/15k what changes as you go upscale is the circuit impeadance (the ability to load the circuit without significant loss of voltage).
If you only want to drive a PIC input pin and not light leds or run motors then use the larger (higher resistance) resistors, that way if you mess up your code and cause an input to become an output, set to low, you will not create a big short.