These programs are free, some are commercial programs but with few or no limitation's. They generally do not have all the features of systems like SolidWorks but are fully functional.
3D
Onshape - From the original creators of Solidworks
Fusion 360 - Finish 30 day trial and register as a START UP. After one year it will ask if you are still a START UP. Answer YES, you must repeat this annually.
2D
These are commercial grade 2D programs.