Not to be confused with the Death Notice, the South African Death Certificate is a much briefer document. The piece of information it offers which does not appear on the Death Notice is the cause of death. This is given by the doctor in attendance, and includes duration of the final illness.
The only way to acquire an official copy of the Death Certificate is through the Department of Home Affairs. When ordering, ask for a FULL certificate, unless you need the certificate for certain visa or other legal purposes in which case obtain a VAULT copy. If delegating to a researcher, mention the reason for wanting the certificate.
In the SA context, pause for thought before embarking on the ordering of any certificates (birth, marriage or death). There is generally a waiting period for the ordering process to grind through the Department’s mill. If you have located a Death Notice for the ancestor it may not be worthwhile pursuing the Death Certificate.