Every time I try to open a pdf file in my web browser I get a message saying "The Adobe Acrobat/Reader that is running cannot be used to view PDF files in a web browser. Please exit Adobe Acrobat/Reader and exit your web browser and try again."
Any ideas what's wrong here and how to fix it?
Check if the Reader add-on is installed / enabled in your browser.
If you state what browser you use, someone may give you more detailed information.