PPD is the abbrevation of Pay Per Download which is a source for publishers to earn some good amount of cash for his/her skills,traffic etc
Well PPD network is a source through which publisher's get paid online for uploading there files and sending them to people to download them and on other side it is an online advertising model where the advertiser's pays the PPD network for advertising their offer
Whenever a visitor visit to your PPD link to download your provided stuff it will show list of surveys/offers and they have to complete the survey before they able to get the stuff downloaded. Click here
learn how to make money with PPD network.