Work offline in Google Drive on iPad
There is a link in the article you mentioned where it says the following: 


  "The Google Drive app for iPhone and iPad lets you view items you've stored in Google Drive with your device even when it isn't connected to the Internet or a mobile network. Offline editing isn’t currently supported."


Emphasis added

http://support.google.com/drive/bin/answer.py?hl=en&amp;answer=107975