Export docx to PDF via XSL FO, using FOP

Please see instead https://github.com/plutext/docx4j/tree/VERSION_11_4_10/docx4j-export-fo

Up until docx4j v3.3.0, this was part of docx4j itself. From 3.3.0 to 6.1.x, it was an optional separate sub-project.

docx4j will use export-FO automatically if it finds it in your classpath.

v6.x series is the last which will support Java 6.