There's no guide for this but the process is simple. You may launch the latest version of the cloud image via a Launchpad. Then, when the instance is running, you should connect via SSH and stop the services by running the following command:
sudo /opt/bitnami/ctlscript.sh stop
Rename the stack directory:
sudo mv /opt/bitnami /opt/bitnami.bak
Afterward, upload the old stack installer to the instance and complete the installtion of the stack as
Hope it helps.