That largely depends on what QlikView licenses you have installed. Do you have a Publisher license? Then it can be as simple as (manually) distributing to those users only that should be able to see/access your document.
If you do not have a Publisher installed, you may want to manually assign Authorizations (EE server in DMS mode) or tweak NTFS file rights.
But IMHO the best long-term solution is to start using Section Access. Read more here: Section Access
It's up to you.