Could this please be made clearer in Affinity Publisher's "help" or even on the PDF dialogues?
I needed to create a multi-page A5 folded brochure.
My commercial printing service wanted the PDF to contain "separate pages" rather than "spreads." As someone who is new to commercial printing, it was not obvious how to translate the language of the printer's requirements into language used by Affinity.
To clarify:
Affinity's "All Spreads" PDF exports eg. facing pages of a booklet as double-page spreads; but how they are viewed... ie. not arranged for printing.
Affinity's "All Pages" PDF exports eg. facing pages of a booklet as a series of single pages, in consecutive order.
Unlike PagePlus, Affinity Publisher does not appear to have a mode which exports pages arranged to suit printing.
See also: https://forum.affinity.serif.com/index.php?/topic/94177-export-pdf-as-an-a5-booklet/&tab=comments#comment-501002