You could try this:
Connect the driver (on the PC that does the printing) to FILE: from Printer Properties > Ports. It will then ask for a file name and you can inspect that file.
Another thing you can try is to stop the normal print queue files from being deleted. With the normal port selected, go to Devices & Printers. Right-click the printer and select Printer Properties. Click the Advanced tab and then tick the box for "Keep printed documents". That way the print job will not be deleted from the queue. This needs to be done on whatever system the queue is. If the PC prints via a server, then it's the server. If the PC prints direct (TCP/IP, USB, parallel,,,) then you need to do it on that PC.
Of course, all of this assumes that the program prints using Windows drivers. If it doesn't then all bets are off.