An improved application sharing system and method allow sharing of documents on a per document basis rather than on a per application basis, in order to simplify the user experience and to provide a more secure sharing environment. A window marking method is used to construct a window list describing the shared and unshared status of various windows. In an embodiment of the invention, a viewer machine displays only a most recently active shared document window even when other windows are also marked as shared. In this way, a viewer's attention can be automatically focused on a current document of interest.