In　this　paper,　we　present　a　novel　steganographic　technique　for　hiding　data　in　a　kind　of　PDF　texts.　We　first　point　out　the　secret　channels　in　a　kind　of　PDF　English　texts,　which　are　generated　from　documents　that　make　the　texts　justified　to　occupy　the　full　line　width　and　position　each　character　individually.　In　succession,　we　describe　our　steganographic　system　PDFStego　in　which　several　strategies　are　applied　to　improve　security,　such　as　making　use　of　redundancy　to　complement　security;　constituting　two　chaotic　maps　to　meet　the　Kerckhoffs　principle　and　to　prevent　statistical　attacks,　and　applying　the　secure　hash　algorithm　to　enable　integrity　service　and　blindly　extracting　service.　Moreover,　we　define　the　embedding　capacity　of　our　system.　PDFStego　can　be　used　to　exchange　sensitive　data　securely　or　to　add　copyright　information　to　the　PDF　files.