The document discusses determining the appropriate image size by considering pixels, dots per inch (DPI), and inches. It notes that pixels are the number of dots that make up the image file, DPI is the number of dots per inch, and inches is the actual printed or scanned size. It also provides limitations for images on the web of 500x700 pixels, 72 or 96 DPI, and maximum sizes of 6.94x9.72 inches at 72 DPI or 5.21x7.29 inches at 96 DPI. Steps are outlined to prepare an image by first determining the desired web size in inches, then saving and compressing the image file accordingly.