I read a forum post about using PosteRazor to make battle maps from the actual maps in the modules. I forgot to bookmark the forum post, but Posterazor can be downloaded from here:
PosteRazor - Make your own poster!
So if you buy the PDF of the module you're running, you can copy the map images out of the the document, and then bring it into PosteRazor. It will rescale the image to several pages in size. It then saves the images as a PDF file. You print out the page, and tape them together. Bingo! A battlemap that looks just like the map out of the module.
You need to pull the image into a graphics editing program like Photoshop or The Gimp and then crop the map to the outter most walls. If you're really good, you'll also use the graphics program to remove all the monster markers and secrets from the image before you run it through Posterazor.
To choose the size for PosteRazor to use for scaling, just count the number of squares on the map. So if a map is 30 squares by 20 squares, then tell PosteRazor to scale it to 30 inches by 20 inches ( you may have to add a half inch or so for the outter walls).
