I need to print off a poster I've made in PhotoShop for an assignment, but I have no previous experience with large format printing. I want to make sure I get it right the first time so I need some clarification on the specs for preparing the file for printing. It's going to be A1 and full colour. As far as I'm told, the resolution should be 300 dpi, but I don't know if the actual canvas size needs to be A1, I currently have it set to A3 because the font was coming up too small. Also, how wide should the margins be? Any other feedback will also be appreciated. If it makes any difference the printer will be an HP Designjet 800. I don't need to send the file anywhere I can print it myself, I just need to know the specs for the document.