AbleCommerce Shopping Cart Software

I need to add some custom user data such as social security number (here in Brazil is CPF), custom fields to address, among others.

Is it possible to do this without having to change the tables / columns in the database?

Thanks,

You can use user settings to store a user specific information without modifying the database columns etc. Please read the following post.
viewtopic.php?f=42&t=8215