TurboTax minimum system requirements for Mac - https://ttlc.intuit.com/community/system-requirements/help/minimum-system-requirements-for-turbotax-mac-software/01/25609
Find download using Mac - https://ttlc.intuit.com/community/installing/help/find-your-turbotax-for-mac-software-download/01/25584
Install TurboTax for Mac - https://ttlc.intuit.com/community/installing/help/how-do-i-install-the-turbotax-software-for-mac/01/26067
Troubleshoot install for Mac - https://ttlc.intuit.com/community/installing/help/turbotax-for-the-mac-installation-troubleshooter/01/25810
If you downloaded the pdf then any pdf reader can open it. The TurboTax .tax2019 data file can only be opened with the TurboTax 2019 software installed on your computer (any state software must also be installed).
If you downloaded the .tax2019 file you need the 2019 program installed to open it.
After you get the program installed the first thing to do before you open your tax return is to update the program and install any state programs you had. You have to first update the federal program before you can download the state program. Go to menu item Online then Check for Updates. If that doesn't work try the manual update. After you update then close the program and reopen it. You might even reboot your computer.
Then open your file. So you first might need to start a fake return to be able to download the state program (go to FILE - NEW). Enter some basic information, then go to the state tab and download the state program. Then try to open your existing return, go to FILE - OPEN