Why edges come out blank
A printer leaves a margin along each edge of the paper, and it can only print inside those margins. The size of the margin varies by printer and paper. That is why a printed grid usually stops a little short of the paper’s edge.
Borderless printing
Some printers offer borderless printing on certain photo papers and sizes. To fill the page, the printer enlarges the image slightly, so a little is cut off at the edges. Don’t use it for anything you will measure from.
A margin itself does not change the scale. Choose actual size and measure a printed check line or several grid spaces before using the sheet for measured work. Content outside the printable area may be clipped.