Using CTRL +V in Mail app on Mac Os X
I run into same issue: At work I have to use Windows and at home I use a Mac. I'm sick of having different shortcuts for these basic tasks. Here is my solution for it:

Go to your User folder on your Mac and open the Library directory.

Here you create a "KeyBindings" folder.

Then navigate into that folder:
(Your User folder)/Library/KeyBindings/

Create a file "DefaultKeyBinding.dict" with following lines:

"^v" = "paste:";
"^c" = "copy:";
"^x" = "cut:";
"^z" = "undo:";


Save everything and restart your Mac.

Now, you will have CTRL + x/c/v/z working like it is on a Windows machine.

This will change the behaviour for page down as requested by MadBoy.