XSL:FO - Formatting Objects - Editor

Oxygen offers intelligent support for FO editing and FO transformations which makes it ideal for developing XML-based publishing applications. Oxygen is a multi-platform XML Editor, XSLT/XQuery Debugger and Profiler written in Java. It supports XML, XSL, XQUERY, FO, XSD, RNG, RNC,NRL, DTD, Schematron, WSDL and CSS documents. It offers a powerful and intelligent code insight that guides the user to write valid XML content. The code insight can be driven by a DTD, an XML Schema, an RNG or by the structure of a partial edited document. Features SVN Client and native XML Databases support.

http://www.oxygenxml.com/fo_editor.html