Hi,
All pins are pass-through from one DB25 connector to the other.
The screw terminals have their DB25 pin numbers on the silkscreen next to them.
For example DB17 is DB25 pin 17.
Pins 1, 10, 11, 12, 13, 14, 15, 16, 17 have resistor to Vcc connection fro pullup if needed.
Pins 10, 11, 12, 13, & 15 also have bypass capacitors to GND.
Jeff