If a fillable PDF is created from a Word document (perhaps even if created natively in Acrobat Pro), and it is filled in or signed by a 3rd party tool (e.g. Preview in macOS, iOS, iPadOS), the PDF is no longer rendered correctly in Adobe Reader, Adobe Acrobat Standard, or Adobe Acrobat Pro. HOWEVER it is faithfully rendered in Acrobat for iOS or Acrobat for iPadOS, or in a web browser (e.g. Chrome) or a built-in viewer like OneDrive. To fix Adobe Reader or Adobe Acrobat, you have to turn off the "Show border hover color for fields" but this makes the form not appear fillable (a huge user experience change). This is a bug - if other tools can render the PDF faithfully (including Adobe's own iOS/iPadOS app) then Adobe must fix Reader and Acrobat to do so as well.