Sorry for the delay in response.
Assuming you have Adobe Acrobat installed on the machine, could you please check if there is an update available for Acrobat by launching Acrobat>click Help>select Check for Updates.
You may refer to the following links:
Could you please let me know the product you have on the machine- Acrobat Reader/ Adobe Acrobat?
Which Operating System is installed on the machine?
Please share the complete error message you are getting when trying to open pdfs.
Awaiting your response.