Running multiple PostgreSQL servers on one physical system is possible if it is convenient for your needs.
Once again, make sure you've read the Deciding on a design for multitenancy recipe so that you're certain this is the route you wish to take. Other options exist, and they may be preferable in some cases.
Core PostgreSQL easily allows multiple servers to run on the same system, but there are a few wrinkles to be aware of.
Some installer versions create a PostgreSQL data directory named...