An incremental encoder will send two channels of pulses, phased at 90 degrees. These encoders are easy to hook to the Kanalog or KFLOP boards. An absolute encoder would require alot more sophisticated circuitry to handle.
Your ROD 426 encoder sents TTL signal, (5V) so you can't send it to the GPIO pin without resistors in series to reduce it to LVTTL (3.3V)
I would assume an encoder like that sends a differential signal. If it does, it can be attached to the JP1 or JP2 differential inputs on KANALOG. If it is a single ended output, Probably to JP5 on the KFLOP board.