I always edit my files just before printing using plain simple PAINT.
From Eagle, select File, Export..., Image
From the pop-up window, you need to select the destination of the file, Monochrome, and then the highest resolution your printer can print e.g. 600. I have found the higher you make the resolution, the finer the detail in the *.BMP file. You must remember that this is a GRAPHIC export, and it will export everything that is selected for display. You need to manually change the "display" settings to only show the desired Bottom (or Top) layer, Pads and Vias
Once the file is exported, you need to open it with PAINT, from the menu select "Image" and then "Invert Colors". You can now edit the file as required and print. With all the times I've used this method, I have never had a size mismatch. Just remember!!! *.BMP files are MASSIVE. To transfer the file to another PC, I would ZIP it.
Hope this helps you