Raspi 4 Schematic: https://www.raspberrypi.org/documentation/hardware/raspberrypi/schematics/rpi_SCH_4b_4p0_reduced.pdf
Raspi 4 Mechanical Drawing: https://www.raspberrypi.org/documentation/hardware/raspberrypi/mechanical/rpi_MECH_4b_4p0.pdf
GPIO Pin Descriptions: https://www.raspberrypi.org/documentation/usage/gpio
Documentation: https://www.raspberrypi.org/documentation