Enrolment

I'm not sure what that documentation says, but we routinely use both Paypal AND self-enrollment with an enrollment key in all of our courses that charge a fee.  When a student tries to enroll in the course, the screen provides the opportunity to use either path.  This gives the teacher the ability to provide back door access to the course for colleagues, reviewers, participants in some other activity or conference, etc. just by issuing them the enrollment key.