I've read this forum entry which states that it is not possible to have AddAndCustomizePages work at lower than I site level. I have .aspx pages in a folder and I would like my SharePoint group to only be able to edit a few of them. Is there any work around to do this or am I stuck having to give the group permission to edit all pages on the site?
I believe you are referring to the "Add or Customize Pages" is a permission at the Site Collection level, and yes, is only available at that level. For what I know, for the mentioned issue going with Permissions is the only way (not recomanded though everytime).
Have you considered using sub-site with Unique Permissions to avoid breaking permission inheritance? Long term might prove better for management!