Both the links above discuss the licensing behind KiCAD (GPL 3). However, in the hypothetical situation, if I signed an NDA for a company, then they request me to find a PCB software to develop some PCB and I chose KiCAD, would I have to publicly release the design and layout of the PCB under GPL?
I am just a bit confused on how far the GPL’s reach extends in regard to hardware developed by the open source software.
GPL3 is about the KiCAD software, not what you design with it. Unless you get in and make changes to the KiCAD software and then distribute the software with the changes, then this does not apply to you.
Yes, hermit already answered the question above. You are free to use GPLed software to design products which will not be GPLed. It’s the same for other GPL software; e.g. compiling a program with gcc doesn’t make the programs you build GPLed.