In Pages use the File ? Page Setup menu option. There you'll find a drop down menu for Paper Size. In it will be a list of paper sizes, including envelope types, that your printer supports. Select the envelope size you need, the orientation necessary and go from there.
I am trying to print an envelope via Pages. However, I can find no way to get my printer (OKI CS3400) to change its format to match the envelope - it just prints an A4 sheet with the envelope nicely printed across the bottom of the page.
In MSWord using windows, when going to print a document, it was always possible to adjust the printer itself - but I can find now way of doing that in Pages. Can anyone guide me?