Ryan from Crocodoc here. It is fair to say that we're not the first non-Flash document viewer -- there are some really solid image-based viewers like Vuzit who have been around a lot longer than we have.
What we are the first to do is leverage new HTML5/CSS3 standards like SVG and text transformations to create a fully embeddable document viewer that renders text natively and has built-in commenting, markup, and PDF export functionality.
You can compare the two different approaches used on the same document here:
http://www.vuzit.com/blog/2010/10/vuzit-now-supports-tight-i... (see embedded viewer under bullet #3)