I’ve scaled the printout of an image of it, that is. The reason it wasn’t easy is that there are a couple of annoying problems in the Print Dialog if you are trying to print something scaled to a certain size.
The first is that some applications simply will not allow you to scale the material to be printed there. No Scale option appears in Print Dialog. Pages, Numbers and TextEdit are examples of such applications. At least with Pages and Numbers you can scale the content within the application before printing it. With TextEdit, you are out of luck. Here’s how to pre-scale Pages and Numbers documents.
Pages: Go to File/Page Setup in the top menu bar, not the display size control in the bottom left of the window.
Numbers: In the bottom left of the window click on the Page View Icon, then use the Content Scale Slider to adjust the printed size, not the display size control. 
Even if the Print Dialog does allow you to scale the output there are still a couple of problems.
First, if you click on Scale and enter a new size (you don’t need the % sign), you will not see the change in the preview.
More seriously, if you enter the % size you want, then click on anything else in the Print Dialog, it will print at whatever original scale it had chosen initially, even though you have changed it in the Scale box and the number you entered is still there. Setting the scale has to be the very last thing you do. After you enter a number in the scale box, press Return. Printing will begin immediately, and it will be at the scale you entered.
