You can amend the help that is installed by WDK for Portlets in your portal application and add new help files for your custom portlet components.
When you add a new portlet to portlet.xml file, add a value for the help mode preference. For example, for the portlet DocumentumDrilldown, the help mode is set to the value cabinets:
<preference> <name>help</name> <value>cabinets</value> </preference>
This help value maps to an HTML file that must be located in /app_root_directory/language_code/cabinets directory, for example, /PORTAL_APP_HOME/help/en/DocumentumPortlets/cabinets/default.htm.