Ive been having this issue for a few weeks now and Ive hunted online and found nothing.
I use Indesign CS6 to create ads. The Images in these ads are .psd saved as CMYK or Grey Scale.
I save them as PDF's, and in Preview randomly the PDF preview wont contain a certain logo and some of the images will be in reverse (Negatives) not sure why. But when I open these files in Adobe Acrobat Pro they look normal.
This is an issue because when I send the files they will see them in this preview state and not see the whole file.....
The answer is stop using Preview. It is a substandard PDF viewer for
anything other than plain vanilla PDFs.
Check out what you're exporting when you create the PDFs. It's called
Adobe PDF and while there are many good PDF readers out there, using
anything other than Acrobat or Reader is hit or miss.