Printing this document in a larger format

The problem is that the spreads on pages 2-3, 4-5 etc are actually single-page A4 documents, so you are going to have to make some fairly major adjustments to your printer settings (or indeed to the document itself) to get half of the overall page to print as a single-page A5. Just scaling them down isn't going to work.

One thing you might try is downloading the pdf, opening it with Apple's Preview app as opposed to 'Adobe' (presumably Acrobat Reader?) and using the standard macOS print dialog. Set up for my trusty old Kodak printer, this lets me print two-up on A4, giving the required A5 size for the individual pages:

This is rather more straightforward than the options and settings in Acrobat Reader's custom-made print dialog. You could then physically separate the halves of the spread using a traditional pair of scissors or a sharp knife and straight edge.

Any alternative solution is going to involve splitting out the A4 pages from the original document as single PDF files, importing them into page layout software set up for A5 (Apple's Pages will do it), cropping and adjusting the individual pdfs and then printing the pages from the page layout. I can give more details if you like.

Cheers,

H