Not sure why you are looking for version 8 , I would suggest better to go with current version 11.
Qlik already stopped support for version 8.
For downloading version 11 follow below:
Somebody may have the old installation files lying around on an old server .... So if you have no joy you could try and ask for an old copy on the site.
As people have said v8 is very old, and even moving to v9 was a massive improvement.
It might be worth the extra time upgrading and testing to v11 as you can do so much more now with the later version.