Inventor files into Illustrator?


I wonder if someone can help?...

I have a client who does drawings in Inventor for their business - I am working on their website and we would like to be able to take some Inventor files into Illustrator to play around them.

They cannot export the Inventor files as an eps but can export as PDF, tiff or jpg. I tried the PDF in Illustrator but it is flattened down with a white background so I cannot highlight the outlines of the shape.

They also sent me file formats .stp and .dwfx but I cannot open them.
Does anyone know if there is a way around this?

Can you get the file in DXF format? I'm pretty sure I've imported this format into Illustrator before and it seems Inventor can export as this.
Also, taking a PDF into Illy normally results in about 500 clipping masks! OK I exaggerate but try releasing clipping masks and you may well get to the core shapes