Install Stuffit Expander to decompress the files
In Mac OS X v10.4 or later, StuffIt Expander, which decompresses the StuffIt compression-format file, is not normally included in the OS. (See http://support.apple.com/kb/TA22952?viewlocale=en_US).
Download StuffIt Expander from the following URL to decompress the on-screen manual:
http://www.stuffit.com/downloads/
The software is available for free.
Note: An email address will be required to download Stuffit Expander.
Once installed, the file will be able to be decompressed and used as needed.