You don't like reading the one in the app? The tap and hold to focus bit is mentioned on the Focus and View page, certainly, and possibly elsewhere. It is also demonstrated at about 2:19 into the video, although from a different context.
I've asked why they don't publish the iPad apps' documentation as web pages as it is evidently HTML, using a built-in browser to view it, but apparently I was insufficiently persuasive. They did it with the iPhone app:
http://forums.omnigroup.com/showthread.php?t=10168
Maybe the idea is that no competitor will be willing to spend $40 or $50 to see what features they need to copy? :D
Sending feedback that you want a PDF document is probably the way to make it happen sooner.