How do I print lectures with 4 pages on each printout page (using linux)?

1) first you convert pdf to postscipt:

> pdf2ps lecture1.pdf

2) then you make a file with multiple pages:

> psnup -d -pletter -f -nup 4 -m50 lecture1.ps Mlecture1.ps

3) and then you print it:

> lpr Mlecture1.ps