Can you please update if you are still facing any issue ?
Also Please update your Mojave OS to 10.14.2 and see if issue persists ?
Ayush JainGreg Brock commented
@Ravi Gupta This is happening on my primary. This problem seems to happen when the computer has been "sleeping" for a few minutes. I just woke the computer as soon as it went to sleep and Acrobat did not exit full screen.Greg Brock supported this idea ·Greg Brock commented
I am also having this problem nearly every time I allow the computer to go to sleep. When I wake the computer up and enter my password, the desktop where my Acrobat session was previously has disappeared. I have to click on the task bar icon for Acrobat to bring it to the front and then make it full screen again. This has been happening for all versions of Mojave and Acrobat Pro DC.
Mac OS Mojave 10.14.3
Acrobat DC Pro 2019.010.20098