Not sure about the dxf from the free version but you can do this...

Download and install the trial Pro version. You get several hundred hours with it. You can do your work in the free version then save it. Open the trial pro version and open the free version you saved....From the trial Pro version export a .dxf or .dwg file to desktop. Then you can email it or print it or whatever you want.

This will only work so long as both of you versions are the same....If you update your free version after you have downloaded the trial pro version it won't work anymore as you can't update the trial version.