如何确保我的应用程序永远不会成为“Open In ...”的默认设置

My iPhone app registers itself as an "Alternate" handler for PDF files in CFBundleDocumentTypes, and recently I've started to get complaints from users about the fact that it has displaced iBooks as the default "Open In..." app for PDFs; it seems that iBooks only registers itself as an "Alternate" handler for PDFs too, and that the system is defaulting to my app instead of to iBooks.My iPhone app registers itself as an "Alternate