do you have acrobat or reader installed?
When you ask a question you need to provide some basic information
-Forum quick start https://forums.adobe.com/docs/DOC-5601
Mac or Windows, and EXACTLY which version of the operating system?
Recent Mac AND Windows operating systems have been known to cause "odd" problems
Are you using a computer Administrator account with full read/write permission?
Exactly which version of the program do you have that is causing problems?
What is the exact error message that you see?
attach a screenshot showing which is installed.
describe what you do to try and view a pdf.