Best AD Monetization Platform For PDF Download Sites?

I am running a PDF downloading website for students

I want to monetize download buttons on my website with video ads or something similar (you can suggest for what works as well)

I just want to force users to watch ads before they can download PDfs.

Any suggestions much welcome

If you have Adsense, Google os offering an offerwall, you can lock the pdf file, user needs to see an ad before can access to the pdf.

conexur said:

If you have Adsense, Google os offering an offerwall, you can lock the pdf file, user needs to see an ad before can access to the pdf.

Click to expand...

Thanks... how do I do that.. any tutorial videos??