We tried another document management extension, and when the file preview option is set to use Google Viewer, it only works for public categories and files. If you have to log in to view documents, the Google Viewer doesn't work.
Does DropFiles have a similar limitation? It looks like you are using Google Viewer for previews, so I wanted to know if you had similar limitations.
Also, I want to know if you can do custom modifications to the extension. We need to get user activity statistics, so we wanted to know if that could be added as a custom project?