There seems to be an issue with Adobe Reader affecting some Mac
One thing that can be done to
make the flashing go away is to turn off the “Highlight Color” in preferences.
This will stop the flashing, and text can still be inserted.
To open the Preferences dialog box, choose Edit > Preferences (Mac OS), and select the category of preferences you want to change.
We will do some testing on other versions of Adobe.
It does not appear to be happening when using an older version of Adobe Reader. https://get.adobe.com/reader/