2
Here's one way, but it'll need you to do some programming.
1/ Install SmartProfile (find it on this website - look in the XOOPS News section)
2/ Add a field to it that is editable by admin and has name of file for each user.
3/ Create a simple module (Use XBS Modgen to create the skeleton) that has no user side or admin side but has one block. In that block program a link that looks up the file for the currently logged on user and presents a link to it. The browser will take care of the download.
4/ Install the module and block and off you go.
PS You could shortcut 1 and 2 by naming each user's file with a standard name suffixed by the user id of the user, e.g. userfile1, userfile14 etc etc.