Tina Stimpson offers this tip for sharing Revit models in Autodesk Design Review:
If you need to share your Revit model, export it to a DWF file. Then the DWF file can be opened and viewed in Autodesk Design Review, a free DWF viewer.
Notes from Cadalyst tip reviewer R.K. McSwain: You cannot open RVT files using Design Review 2013. This tip provides a quick workaround. For additional reading related to this tip, check out this old Cadalyst column.