Adobe open and tell the pdf is not a readable file

Product:
Cognos Controller 10.4.2 fix pack 2
CONTRL_UPDATE_version=CCR-AW64-ML-RTM-10.4.2200.70-0
CONTRL_UPDATE_name=IBM Cognos Controller Update
Microsoft Windows 2019 server

Issue:

When run a standard report in Cognos Controller program, the adobe program starts up and give an error message.

Solution:

Change the Cognos Controller server to use the internal pdf viewer.

Steps:
1. Obtain a short amount of downtime (nobody logged onto Controller)
2. Logon to the Controller application server
3. Browse to the folder C:\Program Files\ibm\cognos\ccr_64\ControllerProxyServer
4. As a precaution, create a backup copy of the file:  web.config
5. Use Notepad to edit the file   web.config
6. Locate the section   <appSettings>
7. Add the following line into that section:
    <add key="useInternalPdfViewer" value="true" />
Save the file, and restart the server to test again.
More Information: