Sometimes when I export large maps into a PDF format from ArcMap 10.3, the PDF doesn't retain the colour. I can print maps off ArcMap 10.3 and the maps are perfectly fine. What I mean by that statement is what I see on the screen and the printed versions are the exact same. However, when I export the map into a PDF, the colour isn't the same as what is seen on ArcMap. I've realized that PDF distorts only the layers which uses grey colour; for example, parcel lots and road line network. I am working with only vector layers. I've spent hours playing with the export setting and still haven't been able to rectify the problem. Please assist.