Coolest program name ever: pstops.

even better, it accepts line noise as input. from the manpage:

To put two pages on one sheet (of A4 paper), the pagespec to use is:

2:0L@.7(21cm,0)+1L@.7(21cm,14.85cm)

To select all of the odd pages in reverse order, use:

2:-0

To re-arrange pages for printing 2-up booklets, use

4:-3L@.7(21cm,0)+0L@.7(21cm,14.85cm)

for the front sides, and

4:1L@.7(21cm,0)+-2L@.7(21cm,14.85cm)

for the reverse sides.

pstops is part of psutils.