See Document/view framework overview.
The wxDocManager class is part of the document/view framework supported by wxWidgets, and cooperates with the wxView, wxDocument and wxDocTemplate classes.
A wxDocManager instance coordinates documents, views and document templates. It keeps a list of document and template instances, and much functionality is routed through this object, such as providing selection and file dialogs. The application can use this class `as is' or derive a class and override some members to extend or change the functionality. Create an instance of this class near the beginning of your application initialization, before any documents, views or templates are manipulated.
There may be multiple wxDocManager instances in an application.
See the example application in samples/docview.