There are two blog-entries about this paper (first one, and the second one) in Christian Robert's blog, that are worth reading.
This is the page for the main paper on PC-priors which is available on arxiv.org. The first techreport was published in 2014.
Maybe version 3 is the most readable one.
The code to rerun all the examples in the paper is available here, requiring the most recent testing-version of R-INLA.