Business Requirements in Brazil (São Paulo)

Does a company that is based solely through the web and registered in the US (paying taxes there) need to be registered (with CNPJ) ect here in Brazil if they plan to open in the Brazil market, and potentially make profit from Brazilian based companies? Does it effect it if the website is in Portuguese as well and if there was marketing done for it? However, there would be no actual office here in Brazil.

Where would I find out more about how that works, taxation, and legal requirements?

Any information to help me get some answers to these logistical questions would be great!

Thanks!