Unfortunately, if you forget to set PAGER back to less, man (as well as some other commands) will continue to display all their text without stopping. If you wanted to have PAGER set to cat just once, you could use the env command:

$ PAGER=less
$ env PAGER=cat man man
$ echo $PAGER
less

This time, PAGER was exported to man with a value of cat, but the PAGER variable itself remained unchanged in the bash session.