• Right-click the thumbnail of a PDF file, and then choose Properties.

  • In the file's Properties dialog box, click Change.

  • If you have Acrobat DC or both Acrobat DC and Acrobat Reader DC, choose Adobe Acrobat DC and click OK.

  • If you have only Acrobat Reader DC, choose Adobe Acrobat Reader DC and click OK.

  • In the Properties dialog box, click OK.

  • Now, the PDF files open in Acrobat Reader DC or Acrobat DC.