The following page contains information about GemBox.Pdf version history with links to the release blog post, stand-alone help file in CHM format and online help, and it shows the release and end support dates.
For more information about new features added in each version of GemBox.Pdf, see the following link.
Release date: 2018-07-18 (blog post)
Stand-alone help file: GemBox.Pdf.Help.zip
GemBox.Pdf on-line help: separate window
Previous versions for which support has ended are no longer maintained. You can download the last bug fix for them from the bug-fixes page.
You can continue to use the previous version indefinitely (the licenses are perpetual), but if support has ended, no additional bug fixes will be released.