Passing along a comment posted anonymously on the 3.1 User Install Guide page [1]:
This documentation page is beautiful--visually appealing, easy to read and to navigate, etc. However, would it be possible to make the documentation available in PDF format, too? I do most of my programming on airplanes, and it would be nice to have a version of the documentation that I could download and refer to when I don't have Internet access. [1] cwiki.apache.org/confluence/display/CTAKES/cTAKES+3.1+User+Install+Guide
