If you're printing at home a4 will do. Choose the file that says either a4 or letter.
If you want it all in one sheet, i hear netprinter.co.uk is very good. In that case you should choose the file that says a0 or copyshop.
What pattern is it if you don't mind me asking?
Its the Scirroco Deer and Doe Jumpsuit. Its probably a little advanced for me currently but when I saw it I just had to have it!