AK realized that a free PDF was cannibalizing sales of their $30 physical books ( AK Learning Series ). The FAQ #2 exclusive was essentially a "beta" version of what became their Extreme Weathering hardcover. It is much more profitable for them to sell you the book.
As a special bonus, AK Interactive is offering exclusive content to users of the FAQ 2 PDF Exclusive guidebook. This bonus content includes: ak interactive faq 2 pdf exclusive