Before upgrading to a new version of DITA Open Toolkit, be sure to back up your current version so you can reapply modifications after your Toolkit upgrade. Such modifications might include:
- Specialization DTDs you added to the dtd directory and the corresponding updates you made to the catalog-dita-template.xml file
- XSLT stylesheets you have added to the xsl directory to override the standard stylesheets
- Plug-ins you have installed
- Catalogs for XML editors