Regarding print size and accuracy, just remember that when you create an image that gets printed, it has a certain dpi resolution of pixels / length (inches, cm, etc)
So for example if you are using something like Photoshop, when you create a new image, don't use pixels as the measuring factor. Use inches (or cm, etc). For example, create a 8.5" x 11" image. Set the dpi to something high like 300 dpi (pixels per inch).
Now put your buttons and graphics anywhere in this image. You can place them using inches as the measuring unit instead of pixels. You can just put a button for example 5 inches from the left side. You don't have to use pixels and try to calculate how many pixels are in each inch etc.
Now, when you print on this image, it will print out at exactly 8.5" x 11" and the placement of your buttons and everything will line up exactly where you want them on the paper.
Make sense?