Microsoft released Office 2013 Service Pack 1. The Service Pack is 642 MB size. You can either update Office 2013 via Windows update or can download from the Microsoft download Center.
The Service Pack 1 will improve the compatibility of Office 2013 with the Windows 8.1 and IE 11. It also improved the compatibility with the modern hardware like high-DPI devices and the precision touchpad. Also provides API for third party developers. It provides support for task pane apps in Outlook 2013 and ability to insert and use content apps in PowerPoint 2013 slides.
If the Service Pack 1 update is uninstalled on a computer that is running Windows 8 or 8.1, an Office application tile on the start screen is blank without an application name or icon if the application is pinned to the start screen. To work around this issue, you can repair the Office installation in the Programs and Features control panel.
Read more about the Service pack here