Why are colors in the Viewer different from colors in ArtPro+, PackEdge and Adobe® Acrobat®?
Roughly you could state that PDF editors like ArtPro+, PackEdge and Acrobat® handle their colors as follows: first the color of a certain ink/ink density combination (example: 75% M + 30% Y) is calculated with a profile to simulate how it will print on a certain substrate. Then another profile is used to simulate that color on the monitor you are using. These profiles used are typically configurable and/or taken from the PDF file.
The Viewer has a different way of managing colors.
First the base color of an ink is calculated with a standard (non-configurable) profile. This results into an RGB value for every ink. This means the color of basic inks (example: 100% M) will already look different than in an Editor. The different densities of an ink and combinations with other inks (example: 75% M + 30% Y) are calculated using an algorithm (so not using a profile).
Obviously, this totally different approach will lead to color differences with the editors.
The current approach has been chosen in function of speed and simplicity towards the end user. On a longer term, a color managed Viewer can be expected.