https://www.partitionwizard.com/
You should expect to put up with some nags to buy the full version, but it is certainly not necessary if all you want to do is resize partitions. It is much easier than doing it the manual way in most cases. Some Linux distributions such as Ubuntu will resize your Windows partitions for you when you install them.
I should warn you however that adding Linux distributions even Ubuntu, but especially Debian will often screw up your ability to boot into Windows until you use a free boot repair tool.
https://help.ubuntu.com/community/Boot-Repair
The previous tool usually gets things working again with just the automatic settings, although I make it a habit to always image the entire drive using the free edition of Macrium Reflect whenever I am adding additional operating systems.
The free edition is no longer on Macrium’s website, you have to get it from Major Geeks. Just check that you are using it for personal use only and do not bother to register it.
https://www.majorgeeks.com/mg/get/macrium_reflect_free_edition,3.html
It is the same edition that is included with Hiren’s Boot CD. So you can use it that way as well if you don't feel like installing it in your Windows system.
I have had up to half a dozen operating systems on the same disk, which takes a bit of wizardry. It is definitely safest to use a separate hard drive for each OS. If Linux's Grub and Window's Boot Manager will not play nice together you can instead choose the boot partition using your computer's UEFI/BIOS boot manager when you first start the computer up.
Do you mean a PHYSICALLY separate hard drive? (In the past we would have said "disk", not "drive".) That's what I'd been led to believe in the past.
Openurmind's post above is referring to what I guess would be called "virtual" drives on the same SSD. I'm assuming the Linux installation would also modify it's partition(s) to EXT4 file format?