diffpdf-free software to compare two PDF files textually or visually

DiffPDF is developed by Mark Summerfield, I just compiled it to windows 32 version.
DiffPDF depends on poppler, poppler-qt, Qt4 library.

DiffPDF can compare two PDF files. It offers two comparison modes: Text and Appearance.
By default the comparison is of the text on each pair of pages, but comparing the appearance of pages is also supported (for example, if a diagram is changed or if a paragraph is reformatted). It is also possible to compare particular pages or page ranges. 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. This will make DiffPDF compare pages in the pairs (1, 1), (2, 2), (3, 3), (4, 5), (5, 6), and so on, to (12, 13).

It is open source(of course free software), want to try it on your windows XP/Windows 7, please download here.