Apple Pages: Use a different header for odd an even pages

In later iWork edition Apple made changes to the formats so this is the cause that you can not follow the procedure described in the article that you are referring.

The best way to go around this annoyance would be:

• Open the pages document with your current pages (I assume is the latest Pages),
• Save us some other name but before you do it extend the save us menu using the up/down arrow where you are presented with more choices,
• Select the radio button "Save copy as:" and choose iWork'08 and then save it.
• Go find your new saved document and you are now presented with the "Show package content" additional menu item (on your right click).
• Extract the images (copy them somewhere else).

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.