Ah, didn't think about the "additional documents" section. That makes more sense.
Regarding the 8.5" x 11" paper, that's probably not
as firm as some of the other requirements, but the fact that they've explicitly stated it makes me think that they've gotten really tired of messing with A4 paper. It's not going to stack well with the other applications, and it's going to feel different in their hands. Obviously the writing is what matters, but I'd suggest you exhaust all other options before submitting with A4. International screenwriters find ways to get 8.5" x 11" paper either by having agents/managers print and submit for them, or by just obtaining the paper themselves before mailing.
I'm not sure of your situtation abroad, but I feel like there's got to be some way of getting the paper you need. If Amazon won't ship to you or offer it to you in your area, I know that there's a shop in London that sells 8.5" x 11" paper that screenwriters use. There are also avenues such as
this website that will print, bind, and ship your scripts wherever you need them to go.
Alternatively, you could email your .pdfs to someone in the States, and they could print and send in the docs for you. I'm not sure if you're from the U.S. and currently living abroad or if you have friends back in the U.S. that could help you out, but I'd try your best to fit the submission to all guidelines they provide. While I don't think they'd refuse your application printed on A4 paper, that's just one way you
don't want your application to stick out from the rest. (literally)
P.S. It's obviously a lot of trust to put into a complete stranger, but I'd be willing to help out a fellow aspiring screenwriter if you have trouble finding any other alternative solutions. Inbox me if you do end up needing help, and I'll shoot you my email address.