The following produces a first page with p.1 on the right half, but a blank 2nd page:

\setuppapersize[A5,landscape][A4,landscape] \setuparranging[2DOWN,rotated] \starttext \input tufte \stoptext

That looks okay, except for the blank 2nd page.

This makes sense only with duplex printing. So the second blank page is ok.

\setuppapersize[A5][A4,landscape] \setuparranging[2UP] \starttext \input tufte \page \input tufte \stoptext

produces a two-page document:

p.1: | | 1 | (i.e. blank left half, and original p.1 on the right half) p.2: | 2 | | (i.e. original p.2 on left half, blank right half)

This is ok, too. Print it in duplex (flip over short side) fold it and you will see.

So in case I've confused the directions of 2UP and 2DOWN, I also tried:

\setuppapersize[A5][A4,landscape] \setuparranging[2DOWN] \starttext \input tufte \page \input tufte \stoptext

It produces:

p.1: | | | p.2: | 2 | |

This makes no sense.

\setuppapersize[A5][A4,landscape] \setuparranging[2UP] \starttext \null\page \input tufte \page \input tufte \stoptext

produces the following arrangement, which is close to what I expect:

p.1: | | 1 | (where the original p.1 is blank except for the page num) p.2: | 2 | 3 |

Ok, too. Print it. Wolfgang