If you log into JBoss.org before you can export from confluence it should let you export without any issues as permissions are set correctly. Export each document at a time, rather than one big document from root.
Ramesh, I am logged into, I see my name up right, but I can't export...
Both single pages like Identifiers - Teiid 8.12 - Project Documentation Editor
and structures like SQL Support - Teiid 8.12 - Project Documentation Editor have lots of export options, but I get the permission error...
...weird, nothing changed, not even reauthenticated... but now it works... even for substructures...