The app itself is a paltry 2009 lines of.cs files.
It's built on top of libpoppler/, Gtk#/Cairo, and Banshee's Hyena library. There are likely some bugs, but in my testing it is quite useful and slick already.
Visit the for links to the git repo, tarball and package downloading, user guides, bugzilla, the mailing list, irc, and more. Five days later, I'm proud to present it to you: It can rotate, extract, and remove pages, and supports reordering pages via drag and drop. On Monday I started working on a new app, PDF Mod, for doing simple manipulations to PDF files.