Normally this whole process of creating the PRN file is transparent, you print a document in your favourite application and the paper starts feeding through the printer. There can however be some uses for intercepting and capturing a PRN file before it gets to the printer.
(Lego) Brick Inventory DB. With this application, the user will be able to inventory his / her lego set collection, and build an inventory of the parts in those sets. Main goal of the project is to enable data exchange between different inventorying efforts, essentially connecting those isles together.
From their website: Parts Catalog is a program used to inventory your collection of Lego parts. The main goal is to be able to check 2 list to see which parts are missing. To build your list you could just download certified list of Lego sets and Combine the list.