I just found this here...
Getting Started It is posted under the discussion on the top navigation bar.
You can click on the left to view as PDF if you like pdf version instead of html.
We have very few pdf tutorials on the new site. Most of the content has been migrated into articles, but as Richard said you can convert any article into a PDF by clicking on the View as PDF button.
The post (Tips on locating Nintex Product articles) lists out some of the places where you'll find content, otherwise if you're after something specific the best thing to do is to use the search bar in the top right hand corner.