ArcGIS (10.3) Export to PDF fails (text fonts show up as cryptic symbols - unreadable).

When exporting to JPEG, TIFF or PNG, the fonts show up correctly.
This is after ArcGIS new installation, it worked fine on the old desktop PC. Now Windows 10, on notebook. Same configuration works fine on all colleagues PCs. It looks OK When I use "print" (with PDF creator) instead of "export" from within ArcGIS.

Any suggestion why export cannot provide maps with correct fonts?