Windows 8.1 Update Now Available for Download

Windows 8.1 Update and Windows RT 8.1 Update (also known as KB 2919355) include improvements that make your favorite apps and settings easier to find and use, and provide more familiar mouse and keyboard options.

Details
Windows 8.1 Update is a cumulative set of security updates, critical updates and updates. You must install Windows 8.1 Update to ensure that your computer can continue to receive future Windows Updates, including security updates. For a complete listing of the issues that are included in this update, see the associated Microsoft Knowledge Base article for more information. After you install this item, you may have to restart your computer.

For more info, see What's new in Windows 8.1 Update and Windows RT 8.1 Update?

Download Windows 8.1 Update
If you’re running Windows 8.1 or Windows RT 8.1 and you get updates automatically, you don’t need to do anything: Windows Update will download and install the update for you within the next few weeks. It won’t interrupt what you’re doing except to tell you that you need to restart your PC to finish the installation.

This Update also available for download from Microsoft Download Center. For the download links see: Microsoft Download Center

Once you click on the "Download" button, you will be prompted to select the files you need. Download the files appropriate for you.

System Requirements
Supported Operating System:

• Windows 8.1

Reference
Microsoft: Install the latest Windows 8.1 Update