TL;DR:
sudo su
find /opt/bitnami/apps/wordpress/htdocs -type d -exec chmod 0775 {} \;
find /opt/bitnami/apps/wordpress/htdocs -type f -exec chmod 0664 {} \;
chown -R bitnami:daemon /opt/bitnami/apps/wordpress/htdocs
/opt/bitnami/ctlscript.sh restart apache