Hello,
With HikaMarket, your vendor can configure (and upload) product files directly from the front-end.
Some files can be "private" (only available when you buy the product), other can be "free".
For the rest, it's purely HikaShop related and I know that there are some thread in the HikaShop forum which are talking about that kind of usage.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.