Hi,
In commercial versions of HikaShop you have three registration mode:
1/ registration: same as in the starter edition, the user needs to enter a password and a username so that his account is created.
2/ simplified registration: the password and username are removed and a user account is automatically created for the user (he will receive an email with his login information which is generated automatically).
3/ no registration: the password and username are removed and no user account is created.
If you want your users to access their orders (and download files), you need to use either the mode 1 or 2.
(The registration can be configured in the config under the tab checkout)