Is this the same PDF in the same container field on the same layout? Or are these different in one of these details?
Was the PDF inserted with Insert PDF or Insert Picture?
On OSX, PDFs can be set to Open With - Preview by default, or changed to Acrobat Pro (option when installing Acrobat Pro).
Highlight a PDF on the computer, Get Info (Command + I) change Open With to Acrobat Pro, check  Change default for All. Close Window. Restart FMP. Test.