Kevin,

>Has anyone ever tried to programatically convert PDF files to PCL on-demand? Ideally, as a process with no need for user intervention.

I don't know if this product can handle PCL, but a great little inexpensive PDF utility I have used is QuickPDF. It has a fully-functional demo, and a quick glance at the docs shows a RenderDocumentToFile method that can render to EPS and other image formats. Perhaps that could get you part-way there?

http://www.sedtech.com/isedquickpdf/?page=functions&fid=381&vb=1