Can't you do what you want via the document settings? The printer should just tag along with whatever your page margins are set to, providing they don't exceed the printer's feed-in/out limitations (from memory, it's 12 mm or 1/2").
Try setting up a document template with margins of 18 - 20 mm (3/4") at both top and bottom, and the sides. Save As to your desktop as Template. Whenever you want to prepare a new document, use that template, but thereafter Save As with a different name to your Documents folder (or directory of your choosing). I did that with AppleWorks and Word, both of which worked well with my Epson 800 printer.