For example, if there are two versions of a PDF file, one with pages 1-12 and the other with pages 1-13 because of an extra page having been added as page 4, they can be compared by specifying two page ranges, 1-12 for the first and 1-3, 5-13 for the second. It is also possible to compare particular pages or page ranges. And there's also support for comparing the pages by appearance (for example, if a diagram is changed or if a paragraph is reformatted, or a font changed). By default the comparison is of the words on each pair of pages, but comparing character by character is also supported (e.g., for logographic languages).
It offers three comparison modes: Words, Characters, and Appearance.
