name=4up
modulus=4
scale=0.2125 inch 0.275 inch translate 0.475 dup scale
1=moveU
2=moveR
3=moveL moveD
4=moveR
.
The prolog record contains an arbitrary number of lines of PostScript code to be placed right before the "%%EndProlog" comment in the header. These commands must not effect the graphics state, and should only be used to define functions for use at page breaks. The default header (shown above) defines functions to move the page origin (in terms of pages), and rotate the co-ordinate space 90 degrees left and right. More than one header can be present in a file; the last one found before the desired layout record will be used.
Layout records contain five types of fields. name, modulus, even/odd, <number>, and scale. The name field may contain any number of alphanumeric characters, and is what determines the logical record name. The modulus field must contain a decimal number indicating the number of pages to be placed on a sheet. There should be fields numbered from 1 through modulus, containing the PostScript commands to move the origin to the correct place for that page (relative to the location of the previously printed page). The scale field contains PostScript commands that set up the scaling at the beginning of each sheet. Despite the name, rotations and translations also belong here. The even/odd fields are used to make even and odd sheets print differently. They're not often useful, but they're handy for preparing double-sided output.
Blank lines and lines beginning with a "#" character are ignored.