You should expect the sensor to be almost open circuit when shaded from IR and less than 0.6V when illuminated. All you need is a pull-up resistor (suggest 10K) to ensure the input can rise to supply voltage, it can then be connected directly to the PIC input pin. If interference is a problem, try a capacitor from the output to ground. I suggest a starting value of 1nF. Larger values might help but will also make the circuit less responsive to fast pulses.
Brian.