The online Wiki Help is now the default Help for Autodesk Inventor and LT. If you are online and access the Help, the online Wiki Help displays.
If you need to work offline and need access to the product help, you can download the Help locally to your computer. When you are offline, the local Help will display. Download the Local Help from here: http://www.autodesk.com/inventor-2013-help-download
CAD Managers and IT Managers: If you want to provide the Local Help to your user base, you can deploy the Local Help through the deployment wizard.
For more information refer to the topics in the Installation section: http://autodesk.com/wikihelp-pds-install-2013-enu