You can include a "format file" containing special commands for the presentation of pages. Often revues ask for this.
In order to do this, you create a file in the working directory containing what you want and save it as
format.pln if you use Plain TeX in jPreTeX
format.ams if you use AMSTeX in jPreTeX
format.ltx if you use LaTeX in jPreTeX
This allows you to have different format files in different directories.
Of course you can put your own TeX commands in these format files.