For older versions of Nbu there is no agent to backup PostGreSQL in NetBackup but it is supported using a 3rd party integration with nbu - zmanda.. So if you encounter any issues with the configuration or backup you would need to reach out to them..
Below is a link which should provide you with all the details including the requirements as well as how to perform the configuration and integration with nbu
http://help.zmanda.com/plugins/servlet/mobile#content/view/9568458With newer NetBackup versions we provide an agent which can be installed on the client machine and then use it directly..