When I open a PDF, I'm prompted to download the latest Flash Player. After downloading,I get the following error message: Your Microsoft Internet Explorer browser includes the latest version of the Adobe Flash Player built-in. Windows Update will inform you when new versions of the Flash Player are available
Which windows version you are currently using ?
If you are using Windows 8 or 8.1, then Flash Player for Internet explorer is updated by the windows update by Microsoft so you need to update your Windows to get the latest version of Flash player.
Current version is 18.104.22.168