You can change your page setup and select a really large tabloid paper format (e.g., 11x17) and I'm sure it will work, but that is not what you wanted to hear. The reality is you have designed a layout for your screen, which is a different medium than print. Print medium is going to be smaller than what is on most screens and printers generally have much higher resolution than a screen by a factor of about 3 or more. In today's technology, don't expect that to change soon. But on this point, you might note that operating systems have been experimenting with support of various higher resolution screens. Right now all OS's I know support one resolution at a time except for the Mac's retinal display. But expect to see a lot more about this in the future where our screens may start becoming more dense supporting higher resolutions to better immitate paper. If our printers resolution is the same as the screen, then we will be able to design layouts that are the same size as on the screen.
Unfortunately, time to design a separate print layout. Sorry!