So, if that sounds like something you'd be interested in trying out, then this little tutorial will show you how to do just that (note that I'll be using the free GIMP image manipulation software to do this - so that anyone can give it a try).
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OK then, the first thing you'll need to do (assuming you already have GIMP installed) is download the relevant image from my G+ gallery. Note that in this instance I'll be using a map from the 50 pixel per inch gallery (found HERE).
Once you've done that, simply open that image with GIMP.
Now that's done, you should see a grid overlay similar to that shown in the picture above. However, in order to get this grid to line up with the squares on the map, simply click on the Image menu and choose the Configure Grid option - which will bring up the options shown below.
Here, you simply enter a value of 50 into the Width and Height fields - and the grid overlay should now line up perfectly with the squares of the map in question.
Next you'll need to select the area that you want to print. For the purpose of this tutorial I'm going to select an area of 8x8 squares - as this fits nicely on a sheet of 'US letter size' paper (and also because the map itself can be split into eight such pieces).
To do this, click on the Rectangle Select Tool from the toolbox (it's the one on the top left of your screen), and draw a box around the area you want to print (note that because we have the 'Snap to Grid' option selected, the box you draw will automatically snap to the nearest grid intersection).
Once you've done that, the area you have selected will be highlighted with a dashed line (as shown in the image above).
Then click on the Image menu and choose the Crop to Selection option...
...which will crop the image down to just the part that we want to print.
Then all you need to do is go to File > Print (or hit Ctrl+P) and when the dialogue box appears click on the Image Settings tab and change the resolution fields to 50.
And that's it - this 8x8 section of the map will now print out at a scale of 1 square = 1 inch.
To do the rest of the map simply hit undo a few times (Ctrl+Z) until you get back to the stage before it was cropped, select the next 8x8 section that you would like to print, and repeat the procedure until you have printed out the entire dungeon.
The whole thing might sound a little long winded at first, but it shouldn't take more than a few minutes once you're familiar with the process.