Goetz's File Splitter
If you are looking to split files in order to make them easier to transfer via email or other means, Goetz's File Splitter is the way to go.
The free download version will not work on Windows 10. If you are using an earlier operating system, you can install the full version with the registration code posted to the site.
The command line version is also linked to on the page linked to above in this post. If you download and unzip the file, you'll see an executable file named gfsplit.exe. Simply copy the files you need to split up into the same folder the executable has been unzipped to. Then open command prompt in this folder. Enter the command gfsplit - followed by the file name of the file to be split - followed by a name for the split files - followed by the maximum size of each file.
Individual files that are sequentially numbered will be generated.