You need a macro. Here's the one I use for paste unformatted.
Code:
Sub PasteUnformatted()
'
' PasteUnformatted Macro
'
'
Selection.PasteSpecial Link:=False, DataType:=wdPasteText
End Sub
You can then add the macro to your Quick Access Toolbar and choose one of the icons offered, which you can then click, or, press Alt+ its number on the toolbar from the left. That is, if it is the fourth icon from the left, press Alt+4.
However, I find it easier to use a keyboard shortcut, so that I can use Ctrl+C to copy, then the shortcut (you could choose Alt+V, for instance) to paste unformatted.
You can look up any of these little tasks, the most unusual being the macro creation. It's not actually difficult, but you'll need a good instruction to got into the VBA screen and add it. The rest is a cinch.