The most popular graphical partition manager on Linux is probably gparted, a GTK frontend to the parted utilities and libraries. While this is a fine program, it does not fit in well on a KDE desktop, and the QT equivalent, QTparted, has not been updated for years and does not use the QT4 interface of KDE4.
KDE Partition Manager rectifies that situation by providing a complete partition manager that fits in with the KDE desktop. The program provides all the features you would expect in a partition manager, creating, deleting, resizing and moving partitions. It too uses the parted libraries, so the actual operations performed on your disks are the same as for any parted based program, the differences between the programs are in the user interfaces.
Operating on live filesystems, especially resizing, carries an element of risk no matter what program you are using to do it. Resizing a filesystem while other programs are writing to it makes moving goalposts look good. Such operations are best carried out while the filesystem, partition or even disk are not in use. To help with this, KDE Partition Manager also comes as a live CD that you can boot from and them tweak your hard disk's layout to your heart's contents, secure in the knowledge that nothing else will try to alter it.