Autodesk recently puts the electronic documentation of its CAD software on the web. You can browse AutoCAD help files online in the same way as you do locally, the same applies to Revit and Civil 3D. All these resources are available on the web site docs.autodesk.com.

Unlike the other CAD products, Inventor documentation is downloadable only – you cannot browse it online. The CHM and PDF files which are normally in your Inventor Help folder can be downloaded by everyone.

There are also other new Autodesk web resources for Inventor users – e.g. the Manufacturing Resource Center at:
http://resources.autodesk.com/msd/Autodesk_Inventor