Suddenly, I can no longer open PDF files using Reader or Reader DC. This affects all files. I am able to open them using Safari.
If I understand correctly, that when you are trying to open the pdf doc using Adobe Reader its no longer opens the file or it gives a blank white screen when you open it?
Adobe Acrobat and Reader official update containing the fix for this issue is now available. This update will be automatically pushed to all existing installations of Acrobat and Reader. If you want, you may also manually trigger the update by opening the application and going to Help > Check for Updates.
More information about this release is here: Acrobat Help | Release notes | Acrobat DC and Acrobat Reader DC | Update
Hope this helps.