They are very large and would eat up too much storage. Most of the people read the docs on-line and never print them anyway. Sorry.

However, PostScript versions of some of the docs can be downloaded from omnigate.clarkson.edu, directory /pub/msdos/djgpp/pub; these usually lag behind current versions quite a bit. Other places to look for PostScript versions of GNU documentation are:

ftp://liasun.epfl.ch:/pub/gnu/ps-doc/ (European A4 format)
ftp://primus.com:/pub/gnu-ps/ (US letter format)