You must login or register to view this content. Thats the button too download at the top centre of the screen
it show this after press in : Currently, viewing the file, you can not download.
Recently viewed this file, too many number of users who have downloaded. Please access the file at a later time. Or if the size of the file you are trying to access is very large, if the file is shared with many users, view the file, it may take up to 24 hours until they can be downloaded. If you still can not access a file after 24 hours, please contact your domain administrator.