Yes, you can share swap area with two or more operating systems. To share swap area, create the swap area when you install the first operating system and then when you install the second one, do not create a new swap area, instead just use the first OS's swap area as the mount point for swap area of the second OS.

If you have already installed both OS's, use gparted to create a common swap area and then add it to your /etc/fstab file to automount it at boot-time.

Just in case you would like to know the drawbacks of using a shared swap area, refer this question on StackExchange:

• Ill-effects of sharing swap area