I have looked at the spec sheets of this chip and it states that MAX Voltage on any pin with respect to VSS (except VDD, MCLR. and RA4) = -0.3V to (VDD + 0.3V). They also state that MAX Input clamp current, IIK (VI < 0 or VI > VDD) ± 20 mA.
Where I work our design actually has us bringing 20VDC to 30VDC to RA5 at < 1mA. Our boards work fine for the most part, we do have issues where there are weird offsets being written to the microcontrollers, I nee to figure out why. I am wondering if this 20VDC - 30VDC (at low current) to a pin would cause this. I've contacted MicroChip with this question and have had no luck.