See here for reference: http://okular.kde.org/news.php
The new version includes an option to save annotations to the PDF file itself. That's why I am very eager to try out. Is there any PPA from which I could install this new version?
Edit: Following 808sound's advice I managed to install Okular 0.15 on precise. The dependencies installed with the upgrade caused several issues with other programs. Fixing these issues required uninstalling Okular and downgrading packages that were upgraded with it. You might want to install Okular from the Kubuntu Backports PPA instead, although in this case you won't be able to export annotations to PDF.
See below for more information. Please keep this in mind before choosing the source you want to install the latest Okular from.
Small remark: BlaXpirit's answer will provide you with the latest Okular minus the annotation feature. For this specific functionality to work you will have to follow 808sound's answer.