If I am a few updates behind, do I need to go back and install each update or just the most recent?
I can only answer for Adobe Reader. If you let the automatic update do its job, it will catch up.
Otherwise, some updates are complete, and others need earlier updates. There is no general way to say, and (though people hate to hear this) no substitute for carefully reading the instructions for each, particularly the prerequisite version.
North America
Europe, Middle East and Africa
Asia Pacific