Open Source CAD Software
KiCad
KiCad is a free and open-source, cross-platform software suite for electronic design automation. With KiCad it's easy to make professional PCB layouts with up to 32 copper layers. The schematic editor provided by KiCad allows you to create your own design without limits and then inspect and view your work in the 3D viewer through an interactive canvas.
LibreCAD
LibreCAD is a free and open-source 2D CAD software used 2D modeling. With LibreCAD, users can model 2D objects in a neat and intuitive GUI based on Qt5. The software is available in 30+ languages and works cross-platform for macOS, Linux and Windows.
FreeCAD
FreeCAD is a highly customizable, scriptable and extensible computer aided design software software for the, MacOS, Linux and Windows operating systems. With FreeCad you can model and design real-life objects in 3D through parametric modeling where all 3D objects you design are controlled by parameters. FreeCAD is released as free and open source software under LGPv2+ license, and can be used for commercial and hobby projects alike.