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.
There's a much easier and more effective way to do this: go to System Preferences > Keyboard > Keyboard tab and click the "Modifier Keys..." button.
From there, you can set the Control key to behave like the Command key: