It;s not diffiuclt.
If you CANNOT edit php.ini or htacces I've this tips: You must acces Direct Admin Account. Make 3 browser tabs
1 First open your product (vritual product) in a browswer tab
2 Open you Direct admin in antoher tab of your browser
3 Open you preferences in PRestashop backoffice, by the upload size settings.
Al those Three tabs must open.
Go to your first tab first Ad your uppload virtual product Thisproduct.zip (BUT NOT SAVE)
Go to Direct admin, and settings set on php module version: NATIVE and SAVE
Go to third tab and change te prestahop backend upload size to 600 (megabytes) SAVE.
Go back to the first tab and Click SAVE and STAY... Wait, and now upload is succesfull.
Go back to your php settings in direct admin, and set this to current 7.0 version, SAVE your module set.
You can set back in orginal settings the prestashop backend upload settiings, but' its not nessescsy.
Works in 1.6 en 1.7 PRestashop.