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I've set my Preflight Profile to "Convert to RGB," but it does not convert the RGB in transparency groups
I have my Preflight Profile set to Convert RGB to CMYK, but I still get the error "RGB in Transparency Group" in the report.
The PDF specification states that transparency group color spaces are used "as the color space into which colors are converted" and therefore do not get converted to CMYK by the Preflight Profile. To resolve this, prior to converting to CMYK using the Preflight Profile, you must change the blending color space of the document to CMYK.
Create an Action List or download the Action List below "Change blending color space to CMYK." You can then apply this Action List to your Preflight Profile under the section Action Lists > Changes. This will change the blending space of the transparency group to CMYK and it will convert to CMYK correctly.