PDFnUP software automates the process of 2up'ing or 4up'ing a pdf document, so for example with a/b 2up page 1 is on the left and page 2 is on the right, with split 2up (4 page document) page 1 is on the left and page 3 is on the right, then page 2 is on the next page left and page 4 is on the right.

It has an optional -down parameter for 2up'ing downwards on a page rather than across the page (left, right)
The output page size can also be controlled and the 2nd page position can be offset with margin controls.
Optional -duplicate option for duplicating pages so you get the same page 1,1 left and right output.
Optional -seq sequence file option for custom sequences of pages in output, see examples folder for examples.
The output page size can also be controlled and the 2nd page position can be offset with margin controls.

Simple command line parameters:

Simple 2up the pdf file a/b
e.g. pdfnup example.pdf out-example-ab.pdf -ab
Simple 4up the pdf file a/b
e.g. pdfnup example.pdf out-example-ab-4up.pdf -ab -4up
Simple duplicate the pdf file a/b
e.g. pdfnup example.pdf out-example-ab-duplicate.pdf -ab -duplicate
Simple 2up the pdf file split method
e.g. pdfnup example.pdf out-example-split.pdf -split
Simple 2up the pdf file a/b downwards
e.g. pdfnup example.pdf out-example-ab.pdf -ab -down
Page range a/b 2up
e.g. pdfnup example.pdf out-example-split.pdf -s1 -e10 -ab
2up the pdf file a/b and set new page size and offset right margin
e.g. pdfnup example.pdf out-example-ab.pdf -ab -mediabox 0,0,612,1584 -cropbox 5,5,612,1584 -rightmargin 120

NOTE: first 2 parameters have to be input file / output file or 2nd parameter -f
If your filename has spaces in it then use double quotes around the filename, e.g. "c:my testtest file.pdf"

Wildcards * are not permitted, if you want to process many files then do: dir /B *.pdf > list.txt, then pdfnup list.txt -fout