That software is dead, unsafe to acquire unofficially, and superseded by Trimble’s own free web tool. For 3D modeling without cost or risk, use SketchUp Free in your browser or migrate to an open-source desktop alternative like FreeCAD.
: You can use essential add-ons like Solid Inspector2 for 3D printing or CleanUp3 to optimize file sizes. sketchup 2017 free version