Return an entry from the ViewerPreferences dictionary.
getViewerPreference([in] BSTR pref, [out, retval] BSTR *val)
This function retrieves an entry, specified by pref, from the document's ViewerPreferences dictionary. The returned value is a null-terminated string, and its length is also stored in *length.

Returns a zero-length string if the specified entry doesn't exist, or if the PDF file doesn't have a ViewerPreferences dictionary.

s = pdf.getViewerPreference("Duplex"); MsgBox "duplex = " & s