1. A method for document marking, comprising the steps of: a. obtaining a first text file representing a document; b. obtaining a marking code to be applied to said document; c. identifying each inter-word space in at least a portion of said first text file and changing each said space based on said marking code to generate a signal sequence having changed space lengths including at least first and second space lengths, said space length being a longer space than said second space length, and said second space length being a shorter space than said first space length; and d. producing a second text file representing a changed version of said document having changed space lengths.
1. A method for document marking, comprising the steps of: a. obtaining a first text file representing a document; b. obtaining a marking code to be applied to said document; c. identifying each inter-word space in at least a portion of said first text file and changing each said space based on said marking code to generate a signal sequence having changed space lengths including at least first and second space lengths, said space length being a longer space than said second space length, and said second space length being a shorter space than said first space length; and d. producing a second text file representing a changed version of said document having changed space lengths. 2. A method of generating documents, according to claim 1 comprising the further step of repeating said steps b, c and d using, for each said repeating, a different marking code.