Docker needs to be run by a user with root access or one which is part of a permitted group.
sudo docker [whatever] works in most cases (assuming a user can sudo). However, sudo can complicate things. For example, sudo makes the PWD environment variable unavailable. This is problematic for things like volumes and binding, which sometimes rely on paths relative to where a command is being executed.
A better way is to add users to a group which can run Docker. When you install Docker it creates a group, docker. Simply adding users to this group will do the trick.
sudo usermod -aG docker [non-root user]