You can use manual imposition -- see screen snap. You could also use a 2 stage imposition with the 1st stage imposing pages 1 and 2 in 2 columns. The 2nd stage would impose 3 rows from the 1st stage.
I'm having some difficulty getting an imposition to come out the way I need it to. I have a 2pg PDF that is going into a 6up imposition. I need a column of page 1 and a column of page 2 on the same press sheet. The closest I can get it is this:
1 2
1 1
1 2
But what I need is:
1 2
1 2
1 2
I've adjusted the setup several times using the Page/Increment settings in the Layout tab, but I can't get it to come out like I need it to.