How to insert horizontal line to page headers in Apple Pages

This is possible in Pages '09, so it probably works in Pages '08 as well.

1. Select a heading in your document

2. Open the Inspector (in menu bar click View -> Show Inspector)

   1. Select the Text section
   2. Select the "More" tab
   3. Under "Borders & Rules", click the dropdown that says "none" and select the line you want to use
   4. Below the dropdown select the icon depicting the line above the content

3. Open the Styles Drawer (in menu bar click View -> Show Styles Drawer)

   1. Since the text is still selected, the heading you're using should already be highlighted
   2. Click the arrow beside the style
   3. Click "Redefine style from selection"

Now everywhere that you used that heading will now have a horizontal line over it, and it will automatically appear whenever you insert new headings.

You can't!

You can't insert a section break in a layout document because layout documents don't have sections; each page it its own section. See Creating Sections:

In a page layout document, each page is one section. You can use the predefined sections as they are, or you can modify or remove them one page at a time.