convert pdf to 2up on linux

You can use pdfnup for this purpose. It is a part of pdfjam and used like this:

pdfnup document.pdf --nup 2x1 --outfile document2up.pdf

a2ps can do a number of things with basically anything and print it to the printer. It can also print things 2-up (or 4-up, or 8-up)

For your purposes:

a2ps file.pdf -2 -Pprinter

a2ps delegates some of it's work to pdf2ps, so make sure that it is installed on your system. You also may want to look at the a2ps man page if you want to do some other things with the swiss army knife which is a2ps.