• Fonts must be embedded.
• If OPI is used, the high-resolution image must be swapped into the file and the OPI comment must be removed.
• Transfer functions (TR and TR2) are not allowed. The application fails pages containing custom transfer functions.
• Pre-separated pages are not allowed.
• Spot colors and CMYK are allowed. RGB and L*a*b* are not allowed.
• LZW and JBIG2 compression are not allowed.
• Bounding boxes are restricted. Each page must have a MediaBox that can include either a TrimBox or an ArtBox, but not both. There can be a BleedBox or a CropBox. The TrimBox or ArtBox must be entirely inside the BleedBox or CropBox.
• Halftone issues:
  • Named halftones are not permitted. You cannot use DotShop screening, since the application relies on the halftone name to choose the screening. When refining to PDF/X-1a, the application removes any halftone dictionary that contains a HalftoneName key, including DotShop halftone dictionaries.
  • No Halftone Phase (HTP) key
  • Halftone Type can only be 1 or 5 (no threshold screening is allowed).
• No embedded PostScript and no PDF features beyond PDF 1.3. Thus, transparencies cannot be present. The application flattens transparencies in PDF 1.4 input.
• Annotation use is limited. Annotations are allowed if they are outside the BleedBox or outside the ArtBox or TrimBox if there is no BleedBox. The exception is the Trapnet annotation, which is allowed without restrictions.

Note: The application does not use Trapnet annotations for trapping.
When refining to PDF/X-1a, the application identifies and deals with all of the above issues where possible. If it is not possible to make a PDF/X-1a-compliant file, the application places the page in the Failed queue.