When switching to bookfold layout, Word will automatically adjust the page sizes to fit the paper size. So, while the paper size will remain A4 (switched to landscape orientation), the page size will become A5 in portrait orientation. You should see an immediate change in the on-screen page size.

If you insert a PAGE field in the page header or footer, the page No.s will both appear and print on all pages.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]

OK thanks for your help, I am going to try that out with the text that I have so far and see how it goes. I will report back after the tryout.