The Digital Publishing Suite tools are updated frequently. Whenever there is a new release, the Folio Producer Service is updated on the web. There is a separate installer for the Folio Builder panel so that you can update the panel without updating your tools. Whenever Adobe updates the web client, update the Folio Builder panel to make sure that the web client and the Folio Builder panel remain in sync.
Note that updating the Folio Builder panel does not update your authoring tools.
The Folio Builder panel updates are available on the Adobe Downloads pages:
Windows: Download Folio Builder panel (Windows)
Mac OS: Download Folio Builder panel (Mac OS)
You also have the option of updating the authoring tools when a new version is released. When you update the authoring tools, any folio you publish is not compatible with any pre-v20 viewer version. For v20 viewer versions and later, update the authoring tools, and you can specify the viewer version when you create a folio. See Create a folio.
With InDesign CS5/CS5.5, you may need to revert to a previous set of Folio Producer tools to be compatible with an older custom viewer (v19 or earlier). Uninstall the Folio Producer tools, and then download and install the appropriate version. Older tools are available on these pages:
Windows: Archive of older Folio Producer tools (Windows)
Mac OS: Archive of older Folio Producer tools (Mac OS)