Visual Studio Addin - Finding a Project for a Document

In my Addin, I have a Document Object, Generic or Text.

How can I find which Project Object the Document is contained in - because looking at the hierarchy of parents, and properties/events it does not appear to be possible.

To further clarify; My Visual Studio Workspace has several Projects, but the Active Document may be in a Project other than the Active Project, so I am trying to find which Project the Active Document is in. Also, the Project file itself may not be in the same directory as the documents which it contains.