The aim of this project was to provide a port monitor and a library that allows configuration of the monitor from within Windows XP and Windows 2000 applications, it may or may not work on newer versions of Windows. This project is no longer under active development.
The printer port monitor can receive raw data from the print spooler, do something with it, and send it on to the printer or elsewhere. For example an application could print directly to PDF with or without user intervention. Note that PDF generation requires an external application to do the actual PDF generation.
There are other open source alternatives out there, mainly Redmon and Redmon EE.