If most - or all - of your users are Brazilian, then I'm afraid you'll have a hard time. People here don't realize the value in software/apps.

Offer a full month trial to your existing userbase, and 1 week trial to new users. The Rollbar email is a great example on how transparency can go a long way. Consider offering different pricing plans with different set of features. Power users are more likely to pay more, and casual users can continue using limited features at a smaller price.

Also, as much as I agree with traskjd comment, I don't think it holds true to Brazil. You probably know what I'm talking about. I'm afraid the strategy here must be "price as cheap as you can", unless you are dealing with a very special audience (or with enterprises).

I'm happy to know how this turns out. Consider sharing a blog post with your experience :) Good luck / boa sorte.