Abstract: A security method and apparatus for use in providing an "invisible envelope" for facsimile transmission thereby avoiding the casual reading of documents by persons interposed between the receiver of the transmission and the ultimate designated recipient thereof. Each page of the document is pattern divided into two portions which are individually unreadable in an easy and straightforward manner. The two portions are sent in sequence (i.e. at different times) and then the original document is reconsitituted at the receiving end by the designated recipient employing a transparency overlay process with the two portions. The patterning at the transmitting end may be accomplished by an optical filtering process or may be computer generated as by modifying word processing software or by a separate program manipulating a pre-input document to produce the two portions for printing and transmission. The HideaFAX.TM. process of this invention is applicable to conventional FAX machines without modification.