public sealed class PresentationEventArgs 

{
  ArcGIS.Desktop.Presentations.Events.PresentationEvent.Subscribe((args) =>
  {
    var presentation = args.Presentation; //The presentation that was changed

    //Check what triggered the event and take appropriate action
    switch (args.Hint)
    {
      case PresentationEventHint.PropertyChanged:
        //TODO handle presentation property changed
        break;
      case PresentationEventHint.PageAdded:
        //TODO handle a new page added
        break;
      case PresentationEventHint.PageRemoved:
        //TODO handle a page removed from the presentation
        break;
      case PresentationEventHint.PageSettingChanged:
        //TODO handle page settings changed
        break;
    }
  });
}