The feature is enabled by default. You can test it by yourself.
I note that the documentation says this:
> Shell Integration
> iTerm2 may be integrated with the unix shell so that [blah blah blah]
> How To Enable Shell Integration
> [blah blah blah]
And that does not make it sound as if it's enabled by default. I really don't know. I only started using iTerm2 about three or four weeks ago.