When the attached PDF file is rendered to a JPG image it causes PDFBox to loop forever.
The problem is easily produced using the PDFBox example org.apache.pdfbox.PDF2Image with the following command line options:-
imageType jpg -outputPrefix OUT Hang.pdf
The fault is new to 1.8.4. As a workaround, we are using 1.8.3 which does not suffer.
We have found many such files and have identified this one as I can share it publicly.