When I open a document using WebDAV, generally the system locks it. This seems to work perfectly with Office and OpenOffice documents... However with .txt and .pdf there's a problem. These type of files are not locked when they are opened with WebDAV: this could make sense for .pdf (they are only-read document), but not for .txt.
Moreover, since a pdf is not locked, it could happen the following scenario: I open a pdf with WebDAV and, while I'm reading it, another user changes the main file of that document using the browser interface. Isn't it a conflict? I'm reading an obsolete and no longer existing file...