I have designed a form that fits onto A5 paper in portrait mode. I cannot get
A5 paper for my printer, so I want to print several copies of this form 2-up
side-by-side on A4 paper in landscape mode. But I cannot find any way of
doing so - none of the multi-copy options (include book-fold) work.

For the moment I have taken the easy option of simply creating a 2-column A4
document wher the second column is simply a copy of the first. But I would
like to find a better way, so that I do not have to edit two separate blocks
every time I want to make a change.

(If you do not use international paper sizes, I should explain that A4
landscape dimensions are exactly what you get from putting two A5 portrait
pages side by side.)