The gov/pdf exploit cycle is a classic black hat technique place a highly optimized PDF or take advantage of an open directory on a high DA gov/edu website, use indexing services to send traffic there, and then leave before the human moderators notice. It is a risky process, but if you need to sell something via CPA or affiliate programs, it is well worth the trouble.
This is a an example of the site below , I copied the link
https://tahoe.ca.gov/wp-content/uploads/sites/257/wpforms/tmp/1099f5a21bc9c35f8dc2430430161421.pdf
What's the process