landscape – Set up for typesetting in landscape
The landscape package is long superseded by the geometry package, which has sophisticated controls on page layout.
Maybe you are interested in the following packages as well.
- border: Draw a black border around a Plain TeX page
- cropmrks: Add crop marks to a Plain TeX document
- placeins-plain: Insertions that keep their place
- varindent: Make paragraph indentation match the length of the line above