How to lock download link for profit?

So I have a landing page I created - http://mmofreecourses.blogspot.com/ - and you can see it has download buttons. There's no link attached yet.

I want to lock the link with some sort of offer, so that for people to download the product they have to do something to make me some money.

I will definitely use Adfly, after which I want it to go to some offer or something, and after that, if the person completes it successfully, they get the product.

I'm a total noob with CPA/PPD/PPI.

Can anyone advise on what I should use? A good network that's legit and pays, and pays to Paypal, and has low withdrawal limits?

Thanks

Hello bro! sry i cant give u any advise!!
your blogspot landing page templete is nice... if it free can u give me the templete?