There are actually two HH PDfs floating around, one from the Tempus Fugitives group and one from Bell of Lost Souls.
The Tempus Fugitives one is called "Age of the Emperor - A Rules Expansion for Warhammer 40k". I'd recommend getting that one as it is more recent, includes far more rules and a very well thought out requisition system with very fluffy units, and is far prettier when it comes to layout issues.
If you google "Age of the Emperor", it's the first result that comes up. I didn't want to directly link, but you should be able to get it quickly. Really good one, that.
My brother got himself the Forgeworld book. "Lavish" is the word I would use to describe it. The main issue, IMHO, is the fact that it only covers the "opening shots" and only a handful of legions. The TF one has them all, albeit in lesser detail and obviously non-official, but still very well done.
EDIT: Dang, ninja'd by the Commander.
