SAC means Support Access Code.
The SAC is used to register / access the Support Portal and some other specific pages on the doc and community portals.
The SAC is created for paying customers so trial users do not have a SAC unless their company already purchased other products.
Without SAC customers cannot access downloads.
The knowledge base articles on the support portal can be accessed freely.
As of now (December 2021) some end users on Syncplicity do not know or may not have a SAC.