switch between 8.5x11 and A4 sized pages within the same book?

[Writer]

>I agree that Nadine’s suggestion of two templates is probably best if you have time to work through each document every time you change to check that there aren’t any unfortunate page breaks.  Sensible use of “keep with next” instead of hard “top of page” settings can help of course.

Yes, definitely.

Something else you can try, but this will really depend how your document is formatted, is print the PDF at A4 size. Then, using Acrobat, "reprint" the A4 PDF as 8.5 x 11. The fonts might look a bit small, but I used to do that and no one complained...to me.

Nadine