Good old printing with attachments I assume. This comes up every time we do a CAM implementation.
If the PDF is somewhat static then you can bring in PDF files using the embedded BIP engine. We have a large customer doing this for payment terms on their POs because they refuse to provide a URL to their terms and they operate in about 10 different countries. But the link to the file is coded into the RD with a condition based on company.
What you can't do, as far as I'm aware, is pick up a variable from the XML source and use this as all or part of the file path. So if you're trying to dynamically attach files to the output, as is the case with JDE attachments, then you're out of luck. I believe you can do this with the full OBIEE version of BIP but not the JDE embedded version.
There are now third party products on the market that will do this for you. Other forms software can dynamically in the line the files. We've done it with Bottomline products http://www.bottomline.com/ and also LRS http://www.lrsoutputmanagement.com/ . We have a client that uses BIP to generate their output but then pumps everything through LRS for printing. This is primarily because they needed the output to be PCL rather than PS and that wasn't going to happen with BIP. They use LRS to put the attachments inline and it is a pretty cool product in that it handles all sorts of file types.
Then there's products like the printing enhancement from Asset Management Solutions http://www.amseam.com/ which will update the PDF output and put it back in the folder. This means that the actual BIP output has the attachments and you can see them from the WSJ screen.