Our PDF library provider has finally provided a 64-bit version of their library and we have integrated it into Global Mapper. There are still some bugs, mainly that raster/image export to PDF isn't working yet, but they are supposedly working on that. Everything else seems to work fine. I have placed a new build at http://www.globalmapper.com/global_mapper13_64bit.zip with the change for you to try. Simply download that file and extract the contents into your existing 64-bit v13.xx installation folder to give it a try.
Let me know if I can be of further assistance.
Global Mapper Support