I purchased the 2011 NECH yesterday.
I am using Adobe Reader to open it.
I had to download a plug-in to be able to open it.
The commenting bars are showing in Acrobat Reader, but when I highlight something or add a note it does not save with the file.
I thought I would be able to highlight or make notes without purchasing the full blown Acrobat program.
If I have to purchase Acrobat I will not be very happy with the NFPA as it adds about $250 to the purchase of the electronic version of the NECH over last cycle.