Wanted to add this capability for those out there looking to unify page layouts within a space:
Goal here was to have a table of contents on every page in a given space, but this could be used to render any macro on pages in a given space.
* Navigate to a space, Browse > Space Admin
* In the Look & Feel Section > Layouts
* Page Layouts > Create custom
In velocity templates, you can call a Confluence macro using notation like this:
$helper.renderConfluenceMacro("{toc}")
Depending on where you want this to render determines where you place it. In my case, I wanted the toc to render above the main content section, so I put this after the metadata section but above the main-content section.
Hope this helps!