I am trying to export a layout to either PDF or JPEG which has background imagery that is too dark. I had increased the brightness via the slider found under Image Layer--> Appearance--> Enhancement, and it looked great in the layout. However, when I use the Share --> Export  tool, the resulting PDF or JPEG has not preserved the brightness change and appears very dark. I also tried to Print to PDF, but it failed altogether. 

Preserving brightness settings during export was never a problem in ArcMap 10.x

Any help is appreciated. Thanks!