Notice the 'pathmunge' function. What it does is either prepend or append a single path top the PATH variable, depending on whether or not the 'after' argument is present:
To prepend /some/path to PATH
To append /some/path to PATH
This is similar to other entries in /etc/profile that use this function. Simply make sure to use pathmunge after it has been defined and before it becomes meaningless, that is before the line
And no, it does not make any sense to modify each user's ~/.profile separately. To provide a system-wide setting you should modify the system-wide /etc/profile instead. Commands in it will be executed upon each user's login.