Affinity Publisher for Mac...booklets

[joelheffner]

How do I use Affinity Publisher for Mac to format Letter size paper to produce a 16 page booklet that will fold into 4.25"x8.5" paper.

[AlanPickup]

You start with 16 pages 4.25 x 8.5 then depending on how you will publish it i.e. online, desktop printer or commercial printing (which needs CMYK colour mode) these are usually uploaded ass single sheets.

If using online magazine you can use the same process and the software will create it this is one I do each month for the charity I am involved with https://heyzine.com/flip-book/c52dc9735c.html 

If you are printing you can use the booklet setting in the print function 

[thomaso]

In APub's "New…" dialog you custom set your desired page size (not spread) + activate facing pages.
Just in case: with your given dimensions you will have to cut 1.5 inches after folding.