For professional printing, global colors can be made to overprint. By applying an overprint color to objects selectively you can control overprinting.
About overprinting
Overprinting means that you can print one ink color on top of another instead of, by default, the underlying color being 'knocked out' (removed).
As a professional printing feature, overprint works when publishing PDFs using a CMYK color space and PDF/X compatibility.
You don't need to explicitly make an overprint for black, for black text or black graphics, as this is set by default. On PDF publishing, you can control black overprinting using the Overprint black option in the Export Options panel (for any PDF export options).
An overprint color swatch is indicated by a curved tab in the top-right corner of its color swatch.
You can check if an overprint color has been assigned to an object's stroke or fill by using the Color panel.
In advance of using this feature, consult your print provider for advice on its use.

- On the Swatches panel, -click the global color swatch's thumbnail, then select Overprint.
SEE ALSO:
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