Just save your files from AutoCAD in .v12 .dxf format. If you're AutoCAD is older than v12, then save it in it's newest .dxf format.
Inventor is about $5000, and will require more work than drawing it in AutoCAD. LazyCAM, SheetCAM and Vectric's Cut2D and V Carve Pro all accept 2D .dxf files. With AutoCAD, you draw the part and export the file. With Inventor, you need to create a 3D model of the part first. Then, Inventor creates your 2D drawings from the model. Then, you can export the drawings.