In both versions 9 and 10, the PDF/X-3 output fails when there is an RGB image. As PDF/X-3 allows for RGB tagged/profiled RGB images, this is an issue for print vendors requiring PDF/X-3 PDFs.
The issues as far as I can tell when an RGB image is present are:
- Fails certification
- Resultant PDF does not have an output intent
- RGB image profiles are not processed and incorporated into the PDF (actually, no image type with a profile has its profile hit the PDF)
- Non-profiled RGB images are not assigned a default RGB profile so as to comply with the PDF/X-3 spec