Preview on Catalina fails to select or copy text in PDF
ICYI:

As it turns out, there is apparently an issue in Apple's Preview app. I took this issue up with another representative at AppleCare. Fortunately, this chap was not an arrogant idiot as the first one was. 

I finally got some feedback on my case today. Here's a brief synopsis: 


  I received feedback from our engineers. They confirmed that there is an issue  with the Preview feature in Catalina. They were able to reproduce the issue by testing it on Macs running both Mojave and Catalina and got the same result that you did. This is something that has been reported and will be addressed in a future software update.