What PIC? On some (e.g. 16F88), you can access inputs/outputs of both comparators and use them as inverters.

However, I haven't used the Wiz107SR module you are using, but most serial-to-ethernet modules intended for interfacing with a µC use positive logic. And, the datasheet for the Wiz107SR indicates you should make direct connections with no need to invert. Connect module TXD to PIC RX and module RXD to PIC TX. You may need to jumper RTS & CTS if you are not using flow control (seldom needed for this) but this may be handled in the configuration of the Wiz107SR