Outlook keeps showing the message "Open PDFs in Adobe Acrobat" hovering whenever I get PDF attachmen

Whenever I look at an email that has PDF attachments, outlook pops up a small window with the message "Open PDFs in Adobe Acrobat" (see attached screenshot) hovering over and hiding a small portion of the email, and I have to click the small "x" to close it each time - which is a bit annoying. Any way to stop this small window from appearing every time? (without removing the plugin).