Don't use PDFKit v0.5.4 – it breaks on dead urls
When I upgraded from 0.5.4 PDFKit deadlocked or crashed when an ApplicationController::RouteError occured. If this error happens only because of a broken image link you probably still wan't the page to render and get a PDF with a "missing image placeholder" instead.
I don't know yet in which version (0.5.2, 0.5.3 or 0.5.4) the bug was built in. At the moment I'm doing fine with 0.5.1 and I didn't evaluate any other versions yet.
I will update this card as soon as I know further information (State 4th Nov. 2013).