Take a look in settings/site.ini, there is a lot of settings to tweak the core of eZ Publish there. Ini files in "settings/" is mostly well commented, often with good examples.
The setting you need right now is under '[TemplateSettings]' in site.ini:
# If enabled will add a table with templates used to render a page.
# DebugOutput should be enabled too.
ShowUsedTemplates=disabled
You will also get the path to the file.
For more about ini files and configuration ( also how to override settings for a specific siteaccess or the whole system): http://ez.no/doc/ez_publish/technical_manual/4_0/concepts_and_basics/configuration
For more about how you can override pagelayout.tpl and other templates so you don't have to tamper / edit eZ Publish or extension files:
http://ez.no/developer/articles/how_to_configure_an_ez_publish_site http://ez.no/developer/articles/how_to_skin_an_ez_publish_now_site
