Adobe updates Reader regularly to safeguard your system against malicious attacks through PDF files. If you receive multiple update messages, make sure that the last update is fully installed. Double-click the Reader installer that you downloaded to complete the installation. For information on switching to automatic updates, see Automatic updates | Acrobat, Reader.
Uninstalling, then reinstalling Reader often solves update errors. For help, see one of these troubleshooting articles for Windows or Mac OS.