Single or multiple help buttons for portlet-style UI?
We're building a call center app where there will be multiple portlets on a page, each with its own function. For example, when the call center agent logs in they might see a Work Queue portlet, a Recent Customers portlet and others.
Each portlet represents a different function, and when a customer implements this product for their call center they can choose which portlets their agents will see.
My questions are:
Is it better to have a single help button in the header of the page, or a separate help button for each widget?
If we have a single help button in the page header, is it better to go to a help topic for the page or pop a menu where the user can choose a topic?
Any insights from similar situations would be much appreciated.