Most likely with the downloaded software package. Reach out to the folks that downloaded the software package to see if you can find it there. The Quest Stat site no longer has it.
Also try the "Help" menu in Stat 5.6.2 and see if you find it there.
I know the docs have changes for each version, BUT, I bet if you download the current documentation you'll find 95% or higher of it applies to your version. You can use that as a basis, and then creat your own internal documentation.