You can download Kubuntu in many ways. Choose the one that suits you the most.

Kubuntu 12.04 Release Announcement.

Kubuntu 12.04.2 Release Announcement.

Regular Download

Download Kubuntu CD and USB stick images. For the desktop a 32-Bit version and a 64-Bit version are available.
Download the Kubuntu ISO to create your own installation CD or USB stick. The download process can take a while, depending on your connection speed (the file size is 700MB).
Download Kubuntu

BitTorrent

BitTorrent is a peer-to-peer download network that sometimes allows higher download speeds and provides more reliable downloads of large files. You will need to install a BitTorrent client on your computer in order to use this download method.
You may then use one of the following links to download the Kubuntu images:

• Desktop CD, 32bit
• Desktop CD, 64bit
• Desktop DVD, 32bit
• Desktop DVD, 64bit
• Desktop Alternate CD, 32bit
• Desktop Alternate CD, 64bit

Read more about Alternate CD and Desktop DVD.

Burning a CD or creating an install USB stick

Kubuntu can be installed from a recordable CD (or DVD) or from an USB stick. Then it can be used as a regular operation system, or as a Live image which you can install Kubuntu from. For more information, see Burning ISO Howto and Installation From USB Stick from the Ubuntu Community Documentation website.

Wubi - Install from Windows

Wubi is an officially supported Kubuntu installer for Windows users that can bring you to the Linux world with a single click. Wubi allows you to install and uninstall Kubuntu as any other Windows application, in a simple and safe way. Are you curious about Linux and Kubuntu? Trying them out has never been easier!
Click here to get the latest Wubi installer (for Windows 98, 2000, XP, Vista, 7).

Kubuntu Active Technology Preview

Kubuntu Active Technology Preview is a preview of Kubuntu using the Plasma Active tablet experience. This is a user interface designed for tablets and is currently at a pre-beta stage of development. Kubuntu Active Technology Preview download.

ARM and Mac Images

Kubuntu is available on other computer platforms. In 12.04 images are available for ARM OMAP and ARM OMAP4. These ports of Kubuntu have received some testing, but are not supported in any way and may well not work for you. Install at your own risk! Kubuntu 12.04 ARM OMAP4 image.

Mac image Kubuntu 12.04 Mac image. See Known issues for installer bug.

More info

About the Alternate CD

The text based alternate installer can be downloaded from the various download methods above. This installation CD is suited for computers unable to run the graphical desktop based installation, either because their computer does not meet the minimum requirements for the live CD or because their computer requires configuration after the installation is complete in order to use the desktop. The alternate installer also includes advanced features such as LVM support.

About the DVD

Do not be confused, even though DVDs can hold far more data than the typical Kubuntu CD, the main benefit of the DVD downloads is to get access to all of the available language packs during install. Most people will be fine with the standard CD installer. The DVD includes both the live image/desktop installer and text based alternate installer.

MD5 Sums

Before burning a CD, it is highly recommended that you verify the MD5 sum (hash) of the ISO file. For instructions, please see HowToMD5SUM.
Below is a list of MD5 sums to check with your downloaded file:

83a4d2843c981e4496380d162a3dda19 kubuntu-12.04.2-desktop-amd64.iso
0636eb276a5a216ca1df201255652d2c kubuntu-12.04.2-desktop-i386.iso