Earlier versions of Delta User Guides are archived as PDF downloads. To confirm your version of the Delta software, in DeltaServer, find About > About Server (or in DeltaGUI: Help > About GUI). The dialog appearance may differ between version of Delta and Windows, but look for the version lines:
Delta 2.4
➢Delta 2.4-19 (January 2017)
➢Delta 2.4-12 (October 2016)
Delta 2.3
➢Delta 2.3-40 (October 2016)
➢Delta 2.3-18 (March 2016)
Delta 2.2
➢Delta 2.2-42 (December 2015)
➢Delta 2.2-25 (July 2015)
Delta 2.1
➢Delta 2.1-4 (March 2015)
Delta 2.0
➢Delta 2.0-5-54 Beta (January 2015)
➢Delta 2.0-5 Beta (November 2014)