Setting the paper size

The papersize is specific to the postscript output device.

position of the text in the sheet

In /etc/papersize:

papersize a4

In /usr/share/groff/1.18.1/font/devps/DESC:

papersize /etc/papersize a4

Commandline:

groff -Tps -P-p -PA4 file.tr > file.ps
groff -Tps -P-p -Pletter file.tr > file.ps

Regardless of how the papersize is specified, the resulting postscript file does _not_ contain a %%DocumentMedia or %%BoundingBox comment. It only has the right position in the sheet.

page and line length

Defaults are for letter paper, regardless of the above. Change to A4 by including the a4.tmac macro file (groff -ma4 …)

These set 1in horizontal margin and 0in vertical margin. To change them or to set for other paper sizes, set them with the .pl and .ll requests, possibly using the previous values \n[.p] and \n[.l] or by setting with + and - to increase or decrease from the previous values, as in page.tr.