It's not an upgrade but just a subscription purchase.If you have a CS4 ,you can get a discount for the first year .
Before buying the subscription ,you can use the trial version to test your files .
You can download CC desktop from this link and install Indesign CC 2014 after :
Some general information for a Cloud subscription
Special Photography Plan
Cloud Plans https://creative.adobe.com/plans
-and subscription terms http://www.adobe.com/misc/subscription_terms.html
-what is in the entire Cloud http://www.adobe.com/creativecloud/catalog/desktop.html
http://helpx.adobe.com/creative-cloud/help/install-apps.html to install or uninstall
Cloud Getting Started https://helpx.adobe.com/creative-cloud.html