Sorry for a dumb question. I couldn’t find it on my searches.
Looking to upgrade to premium. To allow downloading of media to a mobile device. Is there a limit to the number of devices that can download (cache) content?
I want it for my phone and my son’s phone to be able to play my content while offline.
It is not by devices. It is per account. You can sign into as many devices as you want. In the sharing settings for any particular user you share with you can allow syncing in the share restrictions for that shared user
( What there is a limit on is the number of folks you can add to your Plex Home which is 14. Those shared users in your Plex Home will not have to buy the app separately for themselves)
if he has a regular Plex account you added to home, yes he can log in with his own username and password.
if he is a managed user account you would need to sign in with your account once, then use the user switcher to change to his account. (he should not ever need to log out)
It is also recommended you put a PIN on your account.