"The event should be fired when the content changes - e.g. you add/remove/edit a page covered by the index."
Yes, that is what I expected, but it is not happening. I tried updating pages that are specifically included in the indexes I am maintaining. I double-checked that these are part of the index. I also tried manually rebuilding the index. The event for DocumentEvents.GetContent.Execute never gets fired.
"Also, if the changes are made also through the MVC site - e.g. a blog post is added, you also need to deploy the custom module class to the separate MVC application. Otherwise the customized search indexing will not work for content changes that occur through the live site."
I have the custom module as a separate class library. After compiling and generating the .dll for it, I included that dll in both the mvc and cms applications. To make sure that I have done things correctly, I have attached to another even that I know works: DocumentEvents.Update.After. That is simply to test that the module is registered, and it is, because when I save a page, the DocumentEvents.Update.After event gets triggered, but the DocumentEvents.GetContent.Execute does not. All of this is in the same class, so I know for a fact that the module is developed correctly and registered with the site. The only problem is, I don't want or need the DocumentEvents.Update.After event. I need the DocumentEvents.GetContent.Execute event.
What else am I missing? Is there some admin setting that I need to enable?