Checks whether the PDF contains NChannel colors with non-trivial process dictionary.
NChannel is an extension of the DeviceN color space, a multi-component, device-dependent color space. NChannel color spaces give applications greater flexibility when representing colors that are not available on a target device.
NChannel is supported from PDF 1.6 (Acrobat 7.x) onwards. If you are opening a PDF in an earlier version of Adobe Acrobat, colors can print or display incorrectly.
NChannel requires a process dictionary which maps the names used in the colorants list to device colors. This allows giving aliases for process colors.
A "trivial" process dictionary uses aliases that are easy to understand, e.g. maps "Cyan" to the process color "Cyan".
A "non-trivial" process dictionary would use custom aliases, such as "My Process color".