I set form field tab order in Acrobat Pro, but users with Reader get wrong tab order

I have created a bunch of forms with form fields that happen to be set up so that if under the "prepare form" tool, I select, "Order Tabs by Row" everything tabs nicely and I do not have to manually move anything around. But, about half the time, when I send the file to the final user, they open it up in Acrobat Reader and the Tabs from field to field are comepletely messed up.  Extra notes: I am working on a Mac with all software comepletely updated, I have unchecked "Automatically adjust tab order when modifying fields" per other threads. Final users that are using Reader are on PCs. Final users are not in my organization and I have no control over their use or settings. 

thanks in advance,

Amy W