The industry standard is AutoCAD which costs an arm and 3 legs, (too much for an individual) But there is a cheap full featured clone with a freebie trial available. Search for ProgeCAD.
I also have Alibre Pro because that is very different being a sort of cheap version of SolidWorks. The cheap version of Alibre, or whatever it calls itself, is 32 bits so you don't get multi processor 64 bit speeds.
I find the problem with the AutoCAD approach to making an STL is that you specify the entities resolution when you draw it rather than when you export. Editing is not really an option, you have to start over. PITA