Ok, looks like I confused myself a bit 
To clarify, file types like PDF and EXE are used to abuse the service, so they are kind of watched a bit closer, and it’s possible you can be suspended for having them on your site.
From Admin himself:
Basically, since these file types are often used by sites using IF as a storage provider, and there was a deal a (year? Two years?) ago that involved a virus in a PDF file on free hosting, I think while not technically against the rules, they are not allowed here.
Per the ToS point, I mentally switched up the part I quoted above with the ToS, my bad.