How to add button in UIDocumentInteractionController preview

Question

I use UIDocumentInteractionController to preview files:

 interactionController = UIDocumentInteractionController.FromUrl(url); interactionController.Delegate = new UIDocumentInteractionControllerDelegateClass(this); InvokeOnMainThread(delegate{interactionController.PresentPreview(true);} }); 

How to add a custom button at the top of the view to perform any action?