I didn't realize you were wanting to make a newsletter on folded tabloid paper. I thought you couldn't choose tabloid as a paper size in the print dialog.
Booklets is something I've done often. Use
Cocoa Booklet to create a booklet with any number of pages (best in a multiple of 4).
For a folded letter-size booklet start with your Pages document in Legal size & larger than normal font size. Export the Pages document to a PDF & then drag the PDF to the icon of Cocoa Booklet. It will create a new PDF in booklet form.
For a folded tabloid-size booklet create your Pages document in Letter-size as normal & then Export the Pages document to a PDF. Launch Cocoa Booklet & open its Preferences. In Paper Size set the Paper Format to “Personnalisé” with the Width 17 x Height 11 (measuring unit is set in a drop-down menu at the lower left of this preference window. Leave the default margins. In the Destination preference, select Yes for Add a suffix? to avoid overwriting your original PDF & click Save. The choices in the Options preferences are all left unchecked for your tabloid-size document. Then drag the PDF to the icon of Cocoa Booklet to will create a new PDF in booklet form.
