The Nordic Thingy:91™ prototyping platform includes firmware source code, documentation, hardware schematics, and layout files.
The hardware files can be downloaded from the Nordic Thingy:91 product page.
The zip file and its subdirectories contain the hardware design files for the Nordic Thingy:91. The hardware files for the circuit board are available in the following folder in the hardware files zip package:
\Thingy91 - Hardware files x_x_x\PCA20035-Thingy91 Board x_x_x