Here are some symptoms: 1. After Windows 10 update, you open a PDF file. It looks different. 2. You loss some PDF features such as security. Some Add-in for example Outlook PDF add-in doesn’t work.
Resolution: After Windows 10 update, the the default open PDF app change to Microsoft Edge. You need to change back. Go to the PDF file. Right click on it and select Properties. in Open with, change to Adobe Acrobat.