Wow, we're really flattered by these posts on HN (Crocodoc co-founder here).
The HN community has been really supportive of us as we've been working on this. Lim Cheng Soon from Hacker Monthly was even kind enough to give us permission to use some of their PDFs to showcase our viewer.
This PDF (HM issue #1) is one of my favorites: http://crocodoc.com/pUY6tB