General troubleshooting

[larry5099]

Has Adobe Acrobat Changed?  If not how do I make Adobe Acrobat Reader the Default PDF Viewer?  Some PDF's open in Acrobat & some open thru what seems to be some other software with a black background & less functionality.  Also, none open automatically anymore.  I am using Windows 7 & Firefox.

[Dean_Utian]

It could be that you installed something else that's associated with PDFs.

Can you right click on the PDF, choose Properties. In the General tab, you should see Opens with and a Change button, where you can browse to change the associated program.

Here are some other links:
https://support.microsoft.com/en-au/help/18539/windows-7-change-default-programs
https://helpx.adobe.com/au/acrobat/kb/not-default-pdf-owner-windows10.html