I am in the process of updating some personal books, and I <think> I moved the location of some .docx files. In any case, I am getting a helpful warning of "file not found." The problem is that there isnt a method to re-link the path to the .docx file. You <should> be able to double click on the file in the PBB and have the ability to search and re-link the file.
EDIT: You should also be able to double click on the file (when it IS found) and have the document open up in its associated program (i.e. Word).