The default print utility does not really work, it's better if you use your ArcGIS Server PrintTools service. If you are an administrator in Portal you can go to My Organization-->Utilities and change the Print Service to your ArcGIS Server version. I still have issues with map services behind security, but the basemaps work fine and will print KML, WMS, etc...The URL you would use is:???ArcGIS Server's preconfigured print service: https://webadaptor.domain.com/arcgis/rest/services/Utilities/PrintingTools/GPServer/Export%20Web%20M...http://resources.arcgis.com/en/help/main/10.2/index.html#//017s00000028000000#ESRI_SECTION1_C094C0BE...