Reviewing 18.104.22.168 (Aug 23, 2015)
While NITRO PDF Reader is a "FREE" shareware program it does provide a reader similar to Acrobat Reader, I found that it does not truly deliver what it said it would. It's PDF "print" feature produces good quality files but about 3 times larger then my old Acrobat 9 does. It did not appear to work well with Office 2010. Just not enough good results to make me try the "PRO" version.
It's a step in the right direction (the PDF renderer service is 64-bit) but the application itself is still a 32-bit process. There is also no real integration with true 64-bit versions of Firefox.