Read your pdf file via
QFile, resource access is
done by prepending the path in the resource with a ":".
Qt does not natively support displaying PDF documents (it can
export them using
QPrinter though). You can do it
through third-party libraries such as Poppler, see
this Qt Quarterly edition on how to do it.
FWIW the resource access information is the docs, and the PDF
stuff I got off Google in 30 seconds. I expect a bit more research
effort for someone with 7K+ rep points.