Reserve

The Reserve metacommand can be used to reserve a certain amount of white space on a page. The format of this command is:
0 !LPUB RESERVE <float>
The float value is in percentage. For example 0 !LPUB RESERVE 0.3 will reserve 30% of space on the page.
The command should be placed right after the 0 STEP command. Example:
...
1 c x y z 1 0 0 0 1 0 0 0 1 partA.dat
0 STEP
0 !LPUB RESERVE 0.3
1 c x y z 1 0 0 0 1 0 0 0 1 partB.dat
...
This will result in an extra space between these steps.