When using the Downloadable files function, I've noticed that it does not work if there is a space in the filename for the document uploaded to the server. When trying to download the document you get a "The page cannot be found" message as the path to the document stops at the space. I've also tested this on the online demo using the file "document upload.txt".
Users often choose filenames including spaces for documents, and this error should be corrected, i.e by inserting standard code spaces in the filename.
Regards