Make sure your driver is in the right location and startup your application server where Pentaho is deployed into
Configuring the Quartz Scheduler:
go to the file solution/system/quartz/quartz.properties and change the line and search for the property "
org.quartz.jobStore.driverDelegateClass". Change that line so that it reads:
org.quartz.jobStore.driverDelegateClass = org.quartz.impl.jdbcjobstore.PostgreSQLDelegate