Pay-Per-Download is an online advertising pricing model where the advertiser pays the PPD network for advertising their offer, then the PPD publishers from the network, upload their files and when people download them, the publisher will make money, along with the PPD network administrators, while the advertiser will get the offer completion in return.
PPD acts like a middleman to CPA as they usually gets their offers from there, and the PPD administrators do also cut a bit of the money every time a file is downloaded.
Unlike CPA which has a gateaway for completion, PPD networks tend to use a download page only. However, it's more and more available to the PPD network users to use different lockers as a custom feature.
