This PDF is a condensed version of the printable rulebook and FAQ for W:I (v1.6). Its not really a quick reference, since its ~15 pages long, but it is comprehensive. It also contains a set of bookmarks that can be used in the PDF reader to quickly navigate the document.

I maintain the Unofficial Rules Summary over at deckbox, and have been putting this condensed FAQ out for a while, but just never thought to put it up here on BGG.