The cost of uploading a PDF of links is probably not much less than the cost of following those links on your own. So I don't think you gain much by leveraging Facebook in this case.
https://news.ycombinator.com/item?id=1
https://news.ycombinator.com/item?id=2
https://news.ycombinator.com/item?id=3
and so on, until 10,000,000? Perhaps Facebook starts opening every link using 10,000 parallel threads. Can you really replicate that from your connection at home? Perhaps even the sysadmin of your victim site has whitelisted all Facebook IP addresses so their crawlers get a free ride.