If you see a 404 for files on your server but you're very sure that the files are there then you may need to set MIME types for certain file extensions used by WebViewer. With IIS you will generally need to do this and the process may vary slightly depending on your server.
Regardless of the documents that you're loading you'll need to add the MIME type for json files (
application/json) so that the UI text is loaded. If you see buttons or labels in the UI with names like
controlbar.fullScreen then that means the json file wasn't loaded successfully.
You'll need to add
xod with a MIME type of
PDF and Office