A lot of the functionality in Paratext 9 is the same, but there have been significant changes to the menus, how windows work and how to open things. Paratext 9 also includes Enhanced Resources, texts with information about the underlying Greek or Hebrew words.
An awkwardness of using Paratext since it began is how the menus change or apply depending on what your active project is. How often have you gone looking for a command, or realized you just ran a check or tool on the wrong project because you forgot what you’d last clicked in? In Paratext 9, this confusion is minimized because the menu commands applying to specific projects are launched from that project window. Menus for global Paratext functions are launched from the top left icon. Menus are not displayed when not needed, giving you more room for text.
Arranging windows of different projects or components was either a tedious manual process, or a fully automatic one if you used a stacked arrangement. In Paratext 9, it is easier to arrange windows than in the manual process of earlier versions, while you can adjust your arrangement to make one window larger and another smaller, which was impossible in a stacked arrangement.
Rather than several different menu commands for opening different things, like a special command to open Biblical Term renderings, another for dictionaries, another for Notes lists, in Paratext 9 all of these things can be opened from the same Open dialog.
Paratext 9 has new enhanced Scripture resources which have been tagged with information about the Greek and Hebrew words found in the source text. This allows lookups to be performed for lexical entries, images, and maps pertaining to the source language text. These resources are being translated into many languages of wider communication. Existing Paratext 8 resource texts are also available in Paratext 9.
The comprehensive list of new features is found here.