You can get any of the Autodesk software if you register as a student, and no you don't need any proof, just say your studying from home. I've just finished studying with the Open University and I got the student version of Inventor, which is basically exactly the same as the official version except you get a watermark around the borders of any drawings you may want to print off. You can still export to .dxf or .pdf files as well.

You get given a licence code which last 3 years, after which you can just re-register and download again.