Is it legal to alter a document after it has have already signed it?

Question Details:

My employer changed a document that I signed after I had already signed it, without my knowledge or consent. When I asked for a copy of the document they handed me a copy of the edited document with my signature on it. Do they have the right to do this? Do I have the right to obtain a copy of the original signed document before they made changes? What if they deny that the original ever existed? I don't have a copy to prove it even existed. Do I have the right to see the original signed copy that was signed in ink not photocopied? Important Notice