When attempting to download a file as guest (not logged in, I was being redirected to the login page and get this message "EDOCMAN_LOGIN_TO_VIEW_DONNLOAD" (notice misspelling). The message is generated by line 201 in the controller/document.php file.
The key was not in the language file, so I added, EDOCMAN_LOGIN_TO_DOWNLOAD_DOCUMENT="Please login to download document" and changed the key in the controller/document file to EDOCMAN_LOGIN_TO_DOWNLOAD_DOCUMENT.
The key referenced on line 205 in the controller/document file, EDOCMAN_LOGIN_TO_VIEW_DOCUMENT, was also missing from the language file, so I added EDOCMAN_LOGIN_TO_VIEW_DOCUMENT="Please login to view document" to the language file.