Resize your /home partition to a lower size so it gives a small space for PCLinux. With the extra space insert the PCLinuxOS Live CD. Just install it like Ubuntu BUT when selecting the place you want to install, install the root in the partition space you just made. You can have the /home pointing to the same one of ubuntu at /home.
So for example it might be like this
/dev/sda1 / 13.97GB
/dev/sda2 451.79GB (It holds inside all the logicals. NO Resize this one)
/dev/sda5 /home 349.00GB (You made a 100GB Partition for PCLinux. 100GB Less Here)
/dev/sda6 2.79GB (The same SWAP. Except if you want to hibernate)
/dev/sda7 100.00GB (Your new Partition for PCLinuxOS)
If you want to hibernate and all that create yet another swap so not to have the hibernated information in swap when you login with the other Distro.
After that when you finish installing PCLinuxOS you should see in the Grub both Distros.
Just wanted to add, With this question in my head: What is grubs (2) role in the suspend/hibernate process? there is now no need for 2 swaps. Grub will resume or tell you which Distro has been hibernated, so to not make a huge problem when booting. So it is almost safe to assume that you can have both /home shared and swap shared also. But need to take into consideration if you hibernated, WHICH one hibernated.