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.

Xournal is an application for notetaking, sketching, keeping a journal using a stylus. It is free software (GNU GPL) and runs on Linux (recent distributions) and other GTK+/Gnome platforms (also support Windows now).
It is similar to Microsoft Windows Journal or to other alternatives such as Jarnal, Gournal, and NoteLab.
Xournal supports annotates PDF(render/import PDF) and export annotated PDF.

It uses libpoppler to render/import PDF, and uses poppler-glib to create Annotated PDF, but it is a pity that it convert the original PDF to image version PDF.

If you meet the similar issues, and do not want to pay for it, please try Free PDF Page Divide Online service,

• I have a few files with 100-150 scanned A3 images that I would like to split into A4 pages for printing
• I have a 2-Up PDF, and I want to recovery it to the original size

it has the same function with my desktop version PDF PageDivide, but limit 10M upload and output.

btw, it is my 2nd Google App Engine application, also bases on modified version iText 2.1.7.