Making art prints using free software is super simple, and you can create any size imaginable to either print at home or send to a professional print shop.
This method will walk you through how to edit the clear photograph I showed you how to take last week using natural lighting (see it here if you missed it) and then format the image for high dpi printing and to include a white border of any size.
I'm using a Windows PC for this tutorial so the photo editing is done on the free software that comes with it. You can use any program you like for that step though. The second part uses paint.net, a free program you can download here, to increase the print quality and create the white border.