By and large you should certainly be keeping Windows Updates switched on to download and install automatically. If a serious new threat should be uncovered, it's the best way of making sure that you're protected. However, there are occasions when applying a new update can cause problems, and here's how you can undo the changes.
Everything you need is in Control Panel. Click Programs and then View installed updates to see everything that's recently been applied to your computer by the operating system. You won't find updates for all of your installed software here, but you will find patches for applications that are closely related to Windows, such as Microsoft Office and Adobe Reader.
If you think that one of these updates is causing a problem—and we'd encourage you to be pretty sure about it before you roll it back—select the relevant entry from the list and click the Uninstall or Change button that will appear on the toolbar above. Follow the instructions on screen to complete the uninstall process, at which point you should be left with an older version of the software. You can check again for updates to see if an improved fix is available but be careful not to simply redo the changes you've just undone.
You can apply the same principle to any driver downloads and updates that have been carried out on your computer. From Control Panel select Hardware and Sound and then Device Manager. Right-clicking on an entry, choosing Properties and then switching to the Driver tab will reveal an option to roll back the driver. If its grayed out, then the driver has not been recently updated, and you can't take a step back.
Again, we'd only recommend taking this step if you know that a new update has caused a problem—the support forums for the applications in question are a good place to check for confirmation. It's a useful trick to have up your sleeve if you're attempting to troubleshoot issues with a computer owned by you or by somebody else. Don't forget there's also the option to roll everything on your system back to the factory defaults—in Windows 8.1, open the Settings charm then choose Change PC settings and Update and recovery to find the available options.