Wonder if the site is compromised or something.

that’s not it, they were documents relating to that text, the same that were also embedded inside of the article - see https://i.imgur.com/OABLReO.png

but i have never seen such behaviour where webpage would trigger the file download on its own without clicking on anything.

now combined with the fact that i had the browser set to automatically open pdf without asking and the fact the pdf can definitely contain malicious code, needless to say i was surprised.