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.

E.g:

public class MyHandler : SecondHandler, IListEventSink
{

   .
   .
   .

   public void OnEvent(SPListEvent event)
   {

               base.OnEvent(event);

        }
}

I mean this hack ... but it will allow you to have a few handlers with separate code etc...