1. A method of printing a plurality of documents based on a text, with alterations of phrases from one document to another in at least one phrase-inserting part of the text, comprising the steps of: storing into a phrase memory plural sets of phrase data representing plural different phrases to be inserted into the respective documents, said sets of phrase data being designated by respective phrase-indicating codes each consisting of at least one character the number of which is smaller than the number of characters constituting each of said plural different phrases; storing into a work memory at least one set of work data comprising selected plural ones of said phrase-indicating codes in such manner as to specify the order in which said phrase-indicating codes are read out, said work data being designated by a working-group code; storing into a text memory at least one set of text data representing a text of document, said text data including said working-group code at a position corresponding to said at least one phrase-inserting part of the text; printing out said text data to produce a first one of said plurality of documents, while upon reading of said working-group code, reading out from said phrase memory and printing out the first set of said phrase data designated by a first one of said phrase-indicating codes of said work data, so as to insert the first phrase into said at least one phrase-inserting part of the text of the first document; and printing out said text data to produce second and subsequent ones of said documents, while printing out second and subsequent sets of said phrase data which are designated by second and subsequent ones of said phrase-indicating codes of said work data, so as to insert the second and subsequent phrases into said at least one phrase-inserting part of the text of the second and subsequent documents.
9. A method as recited in claim 1, further comprising the step of indicating alternately at predetermined intervals said working-group code, and a predetermined number of leading characters of said work data designated by said working-group code, when the working-group code is entered after the work data has been stored in the work memory.