Hi, This is for CS4. I have an object #1 with a fill (say a rectangle). Below that is object #2 with a stroke (say a straight line). #1 and #2 are grouped. Below all objects is object #3 which has a fill (say another rectangle) and that I am using as background. The group's Opacity is set to Normal 100% (default) but I enable the Knockout Group so #1 and #2 don't interact with each other. I then set the group's stroke and fill to overprint! Enabling Overprint Preview, #1 and #2 don't show through each other but the group overprints. This is expected. When I Save As Adobe PDF and view the PDF in Acrobat Output Preview with Simulate Overprint, the group is shown to overprint (as expected) but it appears that Knockout Group is discarded, so #1 and #2 show through each other. I encounter a similar problem with Isolate Blending. 1- Does Saving to Adobe PDF preserve Knockout Group and Isolate Blending when Overprint is enabled? Any help? 2- In Acrobat, Preflight, where can I see the settings that correspond to Knockout Group and Isolate Blending? Presumably, that would be in Graphic Properties for an object, under Transparency, but I don't see any field that corresponds. 3- In this context where the Opacity is set to Normal 100%, is enabling Knockout Group or Isolate Blending for this object processed as Transparency? There is a post, somewhat related here. But my problem is not a viewing problem (which happened to show correctly in Acrobat for this particular post). https://community.adobe.com/t5/Illustrator/Knockout-group-blending-modes-not-exporting-as-PDF-correctely/m-p/9521316#M75386
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