[saluki]

Track by IP and check a hash or text of the pdf to verify each user/IP can only upload a pdf once.

I think $2 is too low, I'd be more likely to sign up with you for $20/mo for up to 10 pdfs. (add larger plans too)

Aren't you being hit with about $0.30 per charge in fees per trans + open ai api costs at the $2 price point?

If they login can you let them see their history for each pdf and go back and ask new questions later?

Building the login and auth isn't so bad if you use something like Laravel or Rails.