33 ble sense schematic

I need to add hardware interrupts from on board sensors. Where can I get the original pcb files? Not just the board pinout.

Did you check there?

https://store.arduino.cc/arduino-nano-33-ble-sense

You can also check the documentation site for information related to the board.
Arduino Docs: https://docs.arduino.cc/hardware/nano-33-ble-sense