When you copy-and-paste you invoke sometimes substantial format changes to
the file. This is true mac or windows.
For instance, copy and paste in Windows usually involves changing the file
format to bmp or wmf. IOW, you copy a tiff or something but AFAIK the object
that gets pasted is a wmf.
If wmf (which I believe to be the more common conversion), it must exist in
rgb colorspace since I don't think there is a grey colorspace with wmf. This
alone could explain what you are seeing. If I'm right, the explanation is
made. If I'm wrong, its not made but it suggests an anvenue to
travel...don't use copy and paste and don't print to an rgb printer (ink
jet, etc)
I've seen similar things (especially serious image degradation) when
multiple instances are used on mac OS where the conversion is usually to
pict...in this case, there's a greyscale pict colorspace whereas there isn't
a greyscale space for wmf AFAIK.
Within a single application, such as using Multiple paste in PageMaker or
step and repeat in Quark or Duplicate in Corel copy and paste usually works
pretty well....but these situations do not involve the OS and its giu core
routines like doing it between applications does.
if 14 years haven't suggested that copy and paste is the wrong way to move
stuff into a layout program, well.....<G>
Another possible way to solve the problem simply. "if the solution to a
problem is not apparent, try to change the definition of the problem and
solve that instead"...In your composite PDF use the object touch up tool to
sleect the rgb image, right mouse button, "edit image" and bam! it's in
Pshop. Correct it, save, and close. the changed image is back in the PDF.
You may need to set your preferences in Acrobat to allow this. there's a
similar functionality for vector objects.