Need to create a fillable pdf that cannot be re-edited

I have created a field fill-able PDF that will be sent to the sales force.

The boss wants them to be able to fill it and save it but not to be able to reedit that new file.

I know I can flatten the file but how can I make it automatic?

Want to force then to Save As and automatically flatten.

I am using acrobat X, most of the sales staff uses acrobat reader X or XI

Way beyond my knowledge or pay grade.

Thanks for any assistance.