I know this thread is old, but I just wanted to share my experience.
I have to admit that most of the proposed solutions are either very complicated or for the technical savvy, or prove to be unsuccessful.
Want my advice on what worked for me?
First, create a new hard disk for the vm with the size that you want the vm reduced to (for example, if the vm actual disk is 100GB and you reduced the partition to say 50GB, I would make the new hard disk equal to 50GB).
From within the vm, clone the primary hard disk to the newly created (I use EASEUS, comes very handy for this).
When the partition has been cloned, stop the vm.
Edit the vm settings and remove the original hard disk. NOW, make the new one use the same config as the original one (for example, same target id if scsi type).
Boot the system. Voila! Your new hard disk provisioned space is now 50GB! Now you can get rid of the vmdk file that holds the original hard disk and save the precious space of your storage!