Follow up:
I ended up having to use AVDocWillClose event instead of AVDocDidClose event. All I need is the path of the document being closed so that I can notify my program which file was closed. Unfortunately I get an exception in the AVDocDidClose event when I try and get the document path from the AVDoc that is passed in.
ASFile pdffile = PDDocGetFile (AVDocGetPDDoc(doc));
ASPathName myname = ASFileAcquirePathName(pdffile);
CString strDocPath = ASFileSysDisplayStringFromPath(NULL, myname);
The exception is raised when ASFileSysDisplayStringFromPath() is called. These same lines of code work with the AVDocClose replacement and the AVDocWillClose event.
Howie