When you start up Adobe Acrobat, you need to sign in (at the upper right) to get the PDF editing features.
Occasionally, this will generate a rather confusing message that you are not connected to the internet. If that happens, do the following:
Uninstall previous versions of any Adobe products. You can also run the Adobe Creative Cloud Cleaner tool.
Sign Out of Adobe Acrobat at the upper right corner (if signed in)
Quit all Adobe applications that are running (Acrobat, Photoshop, etc.). If there is a Creative Cloud application in the System Tray (lower-right corner), click on it (step 1 below) to launch Adobe Creative Cloud and then use the Sign-out option in the upper right corner (steps 2 and 3 below)
Then use the File - Exit Creative Cloud option on the resulting window to quit the Creative Cloud application
Navigate to the Adobe website and sign out (if signed in)
Search for and launch the Credential Manager app on your Windows machine
In Credential Manager, search for and remove any saved credential for Adobe (select the credential in the list and click remove). When prompted, confirm the removal. Do this for all saved Web or Windows credentials that have the word Adobe in the name.
Reboot your computer and sign back in to Windows
Using a browser, navigate to the Adobe website and sign in using the link in the upper right
Enter your userid@uwaterloo.ca as your email address (even if you use a different/friendly address)
Select the Company or School Account option and then follow the normal University of Waterloo log in process.
Launch Adobe Acrobat and wait for the top right corner to show that you are signed in