...: convert, unpaper, tesseract, gs, and hocr2pdf (if tesseract < 3.03). It is known to run on Unix systems and has been tested on Linux and MacOS X. It supports parallel processing on multiprocessor systems.
In contrast to most competing sandwich programs, it performs preprocessing of the scanned images, such as de-skewing or removal of dark edges etc.
For further information please read the manual: http://www.tobias-elze.de/pdfsandwich/index.html