Out of the box, Kirby does not save which user created/edited a page.
Bu you could add a field in the blueprint, where you select a user e.g. as the creator.
This might be helpful:
http://forum.getkirby.com/t/blueprint-how-to-set-the-default-to-the-person-logged-in/327/3
https://gist.github.com/distantnative/f3918ca69173dd38fbd8
Let’s say you added such a field with the name creator
. To collect all pages by one user, you could do something like:
$pages->filterBy('creator', $site->user()->username())