DESC 'paperfile' keyword is not documented

[Jim Avera]

GROFF VERSION: 1.17.2
MACHINE: x86
OS: SuSE Linux 7.3

COMMAND LINE:
  echo "foo" | troff -Tps > /tmp/xx
  grops /tmp/xx >/dev/null

DESCRIPTION OF INCORRECT BEHAVIOUR:
   DESC 'paperfile' keyword is undocumented.

On my system, the following error occurs:
     grops:/tmp/xx:1: can't open `/etc/papersize'

The file /etc/papersize indeed does not exist (in SuSE 7.3),
but this file is not documented anywhere I can find.
I searched all the g* man pages and the groff info files.

SUGGESTED FIX:

Document the 'paperfile' DESC feature in the info files.

(SuSE also needs to fix their distribution to set up /etc/papersize, but
the lack of documentation in groff makes it hard for a normal user to
recover from this packaging bug).