PDFe - DRM Protection for PDF Documents — All About PDF - Your PDF Toolkit
How do I prevent someone from forwarding a PDF? Use VeryPDF PDF DRM Protection to protect PDF files to stop sharing, editing, copying, printing | VeryPDF Knowledge Base
Protected PDF: Create, Open & Print protectedpdf Files with DRM security - Locklizard
How to Remove Adobe DRM From ePub and PDF eBooks | The eBook Reader Blog