Hi there,
Glad to see that you like our product so far . As you thought, uploading a file for each product is definitely possible thanks to the custom fields.
As Nicolas said in the other topic you have to create a custom field of type "file" and applied on the table "item". If you want to check this out do not hesitate to go on the
demo website
to test it by yourself.
Custom fields of type item are available in the Business version of Hikashop and you can look at the
features list
to see the other features of this version.