You need to use this method.

http://trial.autodesk.com/SWDLDDLM/2013/BDSADV/ESD/Autodesk_Building_Design_Suite_Ultimate_2013_English_Win_32-64bit.part01.exe
http://trial.autodesk.com/SWDLDDLM/2013/BDSADV/ESD/Autodesk_Building_Design_Suite_Ultimate_2013_English_Win_32-64bit.part02.rar
http://trial.autodesk.com/SWDLDDLM/2013/BDSADV/ESD/Autodesk_Building_Design_Suite_Ultimate_2013_English_Win_32-64bit.part03.rar
http://trial.autodesk.com/SWDLDDLM/2013/BDSADV/ESD/Autodesk_Building_Design_Suite_Ultimate_2013_English_Win_32-64bit.part04.rar
http://trial.autodesk.com/SWDLDDLM/2013/BDSADV/ESD/Autodesk_Building_Design_Suite_Ultimate_2013_English_Win_32-64bit.part05.rar
http://trial.autodesk.com/SWDLDDLM/2013/BDSADV/ESD/Autodesk_Building_Design_Suite_Ultimate_2013_English_Win_32-64bit.part06.rar
http://trial.autodesk.com/SWDLDDLM/2013/BDSADV/ESD/Autodesk_Building_Design_Suite_Ultimate_2013_English_Win_32-64bit.part07.rar

You just need to use this method.  The important part is setting your referrer (Referring Page) to http://trial.autodesk.com/

http://trial.autodesk.com/SWDLDDLM/2013/BDSPRM/ESD/Autodesk_Building_Design_Suite_Premium_2013_English_Win_32-64bit.part01.exe
http://trial.autodesk.com/SWDLDDLM/2013/BDSPRM/ESD/Autodesk_Building_Design_Suite_Premium_2013_English_Win_32-64bit.part02.rar
http://trial.autodesk.com/SWDLDDLM/2013/BDSPRM/ESD/Autodesk_Building_Design_Suite_Premium_2013_English_Win_32-64bit.part03.rar
http://trial.autodesk.com/SWDLDDLM/2013/BDSPRM/ESD/Autodesk_Building_Design_Suite_Premium_2013_English_Win_32-64bit.part04.rar
http://trial.autodesk.com/SWDLDDLM/2013/BDSPRM/ESD/Autodesk_Building_Design_Suite_Premium_2013_English_Win_32-64bit.part05.rar
http://trial.autodesk.com/SWDLDDLM/2013/BDSPRM/ESD/Autodesk_Building_Design_Suite_Premium_2013_English_Win_32-64bit.part06.rar

This is about 21 gig in total…

www.autodesk.de has an extended post on how to view Revit files for free at this link:
Autodesk – Autodesk Revit Viewer Free

The page reviews the following methods (none of which are very exciting):

For Revit files There are various possibilities.

Display native Revit files
  • Revit installation in viewing mode
Viewing exported data
  • Viewing DWF in Autodesk Design Review
  • DWF viewing in Internet Explorer
  • DWF Viewing into NavisWorks
  • Viewing in NWD NavisWorks Freedom

The English equivalent to the .de page is considerably shorter:
http://usa.autodesk.com/adsk/servlet/ps/dl/item?siteID=123112&id=7290003&linkID=9243099