How to set up 81/2 x 11 document to fold to 5 1/2 x 11?

This is what I wrote some time ago for earlier versions of Pages. It should still work in Pages 5 since the booklet creating is done in another step after creating a PDF.

You'll need to use Create Booklet Service to create a booklet with any number of pages (best in a multiple of 4). You can create the booklet directly from the print dialog after you install the service. For US letter size booklets, I find it best to create them in legal size in a larger font size to make the proportions better. Download the service from the link & run its installer. It will open the booklet in Preview. You will then need to save the new booklet. Don’t just click the Save button. It will save it in a temp folder that is very difficult to find. I just type ⌘ D to go to the Desktop & then I can move the file wherever I choose.

Peggy,

For US letter size booklets, creating the document with a custom page size of 5.5 inches by 8.5 inches will allow you to use the actual font sizes that you want to produce in your output with Create Booklet Service.

The OP, however, appears to be describing a "booklet" where the front page is 3 x 11 and the back page is 5.5 x 11, which I suspect is outside the capabilities of the Service.

True, but you'll have to manually insert page numbers. My complete directions included using linked text boxes but, since linked text boxes are no more in Page 5, I left that out.