One way is to define the style in css stylesheet with media code 'print'
You can include a separate css File for print or one for all media like this:
@media print {
body { font-size: 10pt }
}
@media screen {
body { font-size: 13px }
}
@media screen, print {
body { line-height: 1.2 }
}
I'm not a professional css guy but you should find enouth examples on the web.
Just search for it