your users have to use Adobe Reader or Acrobat.
The MAC-own PDF viewer does not support XFA forms.
Thank you for your response. I have colleagues who have Adobe Acrobat installed on their systems who tell me they cannot open the worksheets. Additionally, there seem to be other steps that even MAC users who have Adobe Reader have to take to open the worksheets. If there are extra steps involved, I need to document these for my users. After all this time, I would think this information would be available somewhere. Any thoughts? Thanks again.
you can make Acrobat or Reader your default program.
Do the following steps.
1. Right-click any PDF file on your system
2. Select "Open with"
3. Select "Other" (the Finder opens)
4. Check the box "Always open with" and then select Acrobat or Reader.
Here an tutorial: