You can actually use the same plug-in (or the same code at least) with the PreloadedDocument index. You just need to assign the Configuration.EventHandlerAssemblyPath to point to your plug-in DLL (the path is either absolute or relative to the index directory).
Plug-ins work the same no matter what does the indexing, be it programmatic, Windows Service, Web Admin, or Index manager.
Best
Jim
-your feedback is helpful to other users, thank you!-your feedback is helpful to other users, thank you!