Problem Flattening From Fields because of embedded font error

Hello! I am trying to flatten form fields of a PDF originally created in InDesign. I recently got a new Mac and have not been able to flatten the fields since, when I had no trouble before. I receive the following error message: This PDF document cannot be made compatible with earlier versions of Acrobat because it contains and embedded font.

I don't know what to do!! Any help would be greatly appreciated.