(pdfjam or equivalent) Custom layout for multiple pages per sheet?

Usecase: Trying to automate some pdf operations using cli-scripts.
Goal: A 2-column x 3-row, vertical-ordered (i.e. page 1 of output should have Col1:1,2,3 & Col2:4,5,6) pdf file.

What I tried was:
pdfjam --nup 2x3 --frame true --noautoscale false --delta "0.0cm 0.0cm" --scale 1.1 Input.pdf --outfile Output.pdf

The only thing is that I cannot seem to find a way to use pdfjam to control the layout.
Is there any equivalent package that would allow passing such an option?