Can I use a MAX232 to communicate between a PIC and a Raspberry Pi?
You can use one "MAX232 type chip" at each end and have proper RS-232 levels between UARTs. The MAX232 is not suitable for 3.3V operation, but there are other similar chips (eg. MAX3232)  that will work properly from 3.3V (as used by the RPi). 

If your PIC is running from 3.3V and the distance is small and you have a common ground you may be able to directly (or with series resistors of a few hundred ohms) connect the "TTL" inverted serial port pins without the extra chips.