While waiting for the index update, try searching from the top of the document. The first hit for Cakewalk.ini is in the table of contents. Clicking that line opens the section on Cakewalk.ini.
The location of the file is documented here
http://www.cakewalk.com/Documentation?product=SONAR&language=3&help=INI_Files.2.html.
Historically the Reference Guide pdf has been created from the help files shipped with the initial release of SONAR. The pdf does not get updated. The local and web based help do get refreshed with every update. There is an open request about the Reference Guide refresh frequency here
http://forum.cakewalk.com/FindPost/3244803