Ever wanted to do this? ... Me too!
Unfortunately there is not a nice way to do this... however if you are able to modify the code there is a way to string a few of them together.
Take the first document library event handler, inherit from the second. Add your code to do what ever you need to. Call your base class.
public class MyHandler : SecondHandler, IListEventSink
public void OnEvent(SPListEvent event)
I mean this hack ... but it will allow you to have a few handlers with separate code etc...