At #4 are enhancements that I would like to see related to PDF support.  Most of these relate to “maps on demand” type Geoprocessing Services that I sometimes develop.

• Layered PDF to have legend item in same PDF layer as map layer it is linked to (I don’t understand why this has attracted so few votes)
• Include PDF as a file type displayed in Catalog window by default
• Layered PDF to support Transparency
• Export PDF maps with Hyperlinks active
• View GeoPDF Files in ArcMap (and Export Maps into GeoPDF too)

If you are keen to see any/all of the above implemented, then I encourage you to follow the links to find corresponding ArcGIS Ideas awaiting your vote.