Hope you are doing well and sorry for the trouble. As described the text appears stacked one letter on top of another.
Is this a behavior with a particular PDF or with all the PDFs that you open in Acrobat Reader DC? Please try with a different PDF file. If the file is stored on a shared network/drive, please download it to your computer and then try to open and check.
What is the version of the Adobe Acrobat Reader and the OS you are using? To check the version of the application go to Help > About Acrobat and make sure you have the latest version 21.07.20091 installed. Go to Help > Check for Updates and reboot the computer once.
You may also try to turn off the protected mode for testing (Win Only) Go to Edit > Preferences > Enhanced Security > Uncheck 'Enable protected mode at satrtup' Turn off the protected view and Uncheck 'Enahanced Security' > Click OK and reboot the computer once. Note: Please turn on the security after testing to avoid any security risk.