public sealed class PresentationEvent : ArcGIS.Core.Events.CompositePresentationEvent<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;
  }
});