It does say in the Get started with the Help page that you need 10 karma points to upload a file. What it also says is does not say is that voting up or down question or answers gives or takes away from that persons Karma points. Usually 10 points per vote (up or down arrows). Additional points, usually arrows) and 15 points, are added to users providing answers points when a user chooses an answer as the best (check mark next to a question or answer).