I use FreeCAD, a free parametric modeller which can import dxf files plus a shed load of other formats. I use it for designing stuff to 3D print.
It's also available in Mint via the package manager plus you can add the FreeCAD repository to your updater so you can keep it current. Check out youtube for tutorials. It's taken me quite a while to teach myself how to use it but being able to adjust some of the dimensions of the things I'm designing, e.g. screw hole sizes, and have the model updated in virtually real time is brilliant.
Play Bonny!