When I opened the document to update it, none of the non-read-only fields are highlited.
Preferences seem to be correct.
This was after acrobat decided to upgrade itself to 21.0 without me asking.
1 - what gives? Why are the fields not highlighted?
2 - does this mean form fields will not be highlited in Reader?
This is a big issue for me and our client.
NOTE - This is partly solved. Had to check "Show border hover color for fields" in preferences.
Does this mean Reader users will not see the document as I intended?
Yes, when they doesn't have enabled this option.
Better question – is the new default for reader to not highlight editable form fields?
Maybe this setting got reset on your machine when the update was installed.
If you want you can even embed some code in your file to switch it on, but you should inform the user before doing so, as it would also affect other files they open.