Built-in XSL-FO Processor
The Oxygen XML Editor plugin installation package is distributed with the Apache FOP that is a Formatting Objects processor for rendering your XML documents to PDF. FOP is a print and output independent formatter driven by XSL Formatting Objects. FOP is implemented as a Java application that reads a formatting object tree and renders the resulting pages to a specified output.
Other FO processors can be configured in the Preferences dialog box.