Alan Britto writes:
If you must render an image for print, there is an Add-on for Blender that you should take a look. It is called “Render for Print” and it features some nice shortcuts for printing images. For instance, we can pick the size and DPI for an image, and the Add-on will do the math for us, and set the size in pixels of the render for that particular paper size and pixel density. And there are lots of presets with paper sizes!