How to convert old Pages documents to Pages ’13

Someone has to give you the bad news:

You can't. You have to copy/paste and re-edit again in the other mode. When you create a new pages document, you have to wisely chose the one that suits you best. You can’t go back and forth between them nor mix the types in the same document.

Sad but true. ;)

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).