How do I make my notebook file size smaller

By default, SigmaPlot uses a fast saving technique that appends rather than rewrites the entire file. The drawback to this is that if large amounts of data are removed from a file, this does not reduce the size of a file.

You can easily force a file rewrite, which can compress a file significantly, simply by choosing Save As ... instead of Save. This creates an entirely new file, which does not contain any of the unused space of a file that has not be completely rewritten.

Alternately, you can enable backup files, which will also cause the file to be rewritten each time.