I had a requirement to setup BI Publisher as a printing server for APEX.
Enabling it would make APEX deliver high rich printing with the help of BI Publisher Engine.
RTF templates that are built from BI Publisher Word Template Builder works good in APEX .
You can follow instructions in the link to setup the APEX and BI Publisher integration.
Refer Section 3.3 Configuring Application Express to use BI Publisher
When it comes to hand written or template builder generated XSL-FO layout there are few limitations and bugs.
An XSL-FO which generates data in the format of tables comes up good when APEX process it with the help of BI Publisher Engine.
But if the XSL-FO layout has a Graph then it never gets processed. There will be a zero-byte PDF file generated when done.
For some technical reasons the BI Publisher Engine does not process the Graph that is in the XSL-FO Code that is loaded into APEX.
But the same XSL-FO layout works find with a graph if invoked from a BI Publisher standalone edition.
Oracle Apex Support group is addressing this issue and it has been promised to get a fix in version APEX version 4.0
BUG 8237966 : PDF PRINTING OF CHARTS FROMAPEX TO BI PUBLISHER WITH XSL-FO LAYOUT NOT WORKING