We're phasing out PDF support in general in SQL Developer. In future releases if you want PDF content, you'll need to use a printer driver to have your machine 'print' the PDF file for you based on the viewer/editor in SQL Developer.
In other words, we won't be enhancing pdf support in reports.
Instead, I would look at generating HTML something along the lines of
http://ba6.us/content/presentations/2014-SQLDev4Reports/DMann-SQLDeveloper4Reporting.pdf -- see slide 42, he also has lots of examples on his site
Or, it may be time to actually start using APEX if you want to generate rich, end user level reports. The reports in SQL Developer are more for ad hoc things, making things in the db easier to access for a developer.