To set the paper size for a worksheet or document, choose Paper dialogue box will be displayed.
from the menu. TheTo choose the paper size, either click on one of the pre-defined paper size buttons, or the
button in the dialogue box. On RISC OS this option is only available if a printer driver is loaded on the icon bar, but if it is you should use it as it will ensure that your document is laid out correctly for use with your printer, as described above.The name of the paper chosen appears in the box marked Paper name. Its size details and the margins needed to define the printable area appear below.
See also Custom page sizes.