What script these websites use?

I just search for some ebooks and these websites always appear with good rankings, here is some examples:

http://bookfreenow.com/download/La_historia_quimica_de_una_vela_(Violeta)/

https://cultivatingeducation.com/DOC-ID/neural-networks-for-pattern-recognition

https://pdfrog.com/download/mandalas-to-embroider.pdf

If you search for a ebook, u find these websites in first page of google or similar websites but i can't download nothing, how these websites get some high in search engines and what script they use, is a good way to make some bucks?

They look like regular doorways. I'm not sure that you can find their script in public access.

Check their backlinks on Ahref or something similar.