Hi - did you have any luck with this. I have the same query ie - I have files which I want to link to that will, when clicked on in the wiki, open the file rather than download it.......
Having tested a few approaches, one that seems to work is to set up an FTP share that does not require login – that is, enable anonymous access to a 'public' ftp area. The permissions need be set to read-only or read/write to all, and files can be linked to in the following format from a wiki page: