When exporting PDF documents in CorelDRAW 2019 there is an error in JPEG compression. Low and high quality has switched sides. When you chose the lowest quality in 2019 you get the best result, when you chose the highest quality you get the worst result. The words low and hight should switch places. Have a look at version 2017 here below, which is correct.
Seriously Corel? What is the deal? Have ALL the programmers been chased off and only the intern is left?
Stuff like this everywhere. Have you tried the Photo-PAINT tone curev on a laptop? Or the duotone curve?
Thanks for reporting this. Others have encountered this problem, too: pdfs export.
Increase the quality; see worse results!