http://www.futaba-rc.com/manuals/index.html

Scroll down and you'll find the 4EX is listed and the manual is available available for free download.

The 4EX is a 4 channel transmitter though, not a 6 channel. The 6EX is a 6 channel transmitter.

The majority of current and recent models are listed, though, so whatever you have should be there.