I have a Page Layout document in Pages currently. Is there a way to convert part of the document into "word processing" mode where when you run out of room on one page, it automatically creates a new page?
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. ;)