"Still, I cannot tell what went wrong when you commented on Untitled-1.pdf"
After a new test this is still true.
Did some of my own comments in my exported PDF/X-3 pdf in Acrobat Pro.
Saved the commented PDF to a new name. Imported the commented PDF to your InDesign document's PDF Comments panel. No comments are missing. Even when I did only one comment in the last word of a line.
Regards, Uwe Laubender ( Adobe Community Professional )
"Still, I cannot tell what went wrong when you commented on Untitled-1.pdf"
This problem is not only on this Untitled-1.pdf. First post example is made from completely different indesign document. And i made another test and it's still the same - Untitled-2 is without PDFX and all comments work. Untitled-3 is with PDFX (i made exactly the same coments in the same way on the pdf) and two comments are missing (to be exact - comment are present in PDF Comments List, but they are not marked in the text).
So in my case PDFX somehow damages PDF Comments. I already changed this to None in the preset - it was only for pdf "first check".
OK, i made a quick test. It's Untitled-1.indd and Untitled-1.pdf. And it works wrong.
Newest Acrobat Pro DC, Export preset is custom, Compression Medium JPG, No Color Conversion but with PDF/X-3:2002 Standard. And this could be possibly the cause of the error.
I made a second Untitled-2 no PDFX.pdf with Standard None and it looks fine.
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