To assign a new or changed document class to a file, use the WebDAV Explorer to display the information on the XML indexing of this file. Choose a document class, and then Update.
If you change the document class of a file, or remove all assignments to a document class (No Document Class Assigned), then the existing index values for this file are deleted, and the indexing status changed accordingly. If you have assigned a different document class to the file, then the file is indexed again automatically, if the corresponding index engine is running.