Typically Pentaho transformations/jobs are executed on a schedule, but to cut down on the delay between the database (pgAdmin) update and work, is it possible to trigger a job to run when the connected database is updated/changed (Such as creating a new PO)? The database is also accessible through API. I attempted to make this happen through an event trigger that creates a Windows event which runs a tasks but I couldn't find a way for pgAdmin to create a Windows event.
There's not a single answer to this, I suppose you could schedule a Pentaho job looking for something else that gets informed when the database is updated, so the job runs every X seconds/minutes/hours/whatever looking for that information, if the information is not found, the job ends, if it's found, the job continues to capture the changes in the database.
Now, the information to look for to trigger the capture, is whatever you can think that you look for or that is similar to something you already have implemented. It could be simply comparing timestamps in a table, or it could be a file available in a certain location that gets moved one the database change is processed and is created anew when there's a new change in the database, you could create an API to handle these changes... there are multiple possibilities, usually you just choose something you are familiar with and create the process.