The actual pinout depends on the mode (SPP/EPP/ECP).
In SPP mode, you have about 13 output pins and 4 input pins (correct me if I am wrong here). 8 of the output pins are specifically data pins and the rest of them are control pins.
Go to Ralf Browns Interrupt Page. He has documentation on port addresses, and it will explain what each address corresponds to.
Because you have about 4 input pins (status registers), use the port that captures the status of these registers, and convert that into 4 bits. You will need to read from the port twice to obtain a full byte (4 bits * 2 = 8 bits = byte)
With EPP and ECP, data transfer with the port is supposed to be easier, but I can't help you further with these modes, because I don't deal with them.