The fix for this issue is available in the latest InDesign update 15.1
Please update your InDesign version to get the fix.
Adobe InDesign team
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After exporting to pdf from Indesign to Acrobat the transparent background around image prints a darker black than the surrounding black background. I've spent tons of time tweaking settings and reading post and could not resolve the problem. I was able to print correctly from indesign once I changed:
-edit-->preferences-->appearance to black-->changed output to print all black accurately
However, from indesign, I couldn't change my printer setting to print 2 to a page and 2 sided so I still needed to print from acrobat. I changed tons of settings in acrobat thinking it had to do with rich black issues or compression issues etc.
I did find a work around that may help to avoid the problem. I went back to indesign and placed a black image over background instead of filling the background with the 'rich black swatch'. I created the black image in fireworks as .png.
When I exported this time, the blacks matched. Maybe someone knows how to fix without using an image but at least this helped get the job done.