solution for driving multiple 7 segment LED display from 3 volt µC
You can avoid the use of external display driver by choosing a PIC with higher pin-count. Driving six 7-segment digits will need 14 extra pins on your PIC. You can multiplex the display in software. Depending on your application you can use a 28 pin PIC (minimum 18 pin PIC that gives you 16 IO) and go higher if your application demands it.

Removing extra variables (like the driver chip) will ease your debugging efforts.

Here (below image) is something that you would need. You just have to add two more displays. You may not need transistors depending on the PIC and display current source and requirements. Make sure you check the current requirements of your display and the current that your PIC can sink.