Existe un programa que permite desproteger los documentos de acrobat, pero es shareware (la versión no registrada sólo muestra las 4 o 5 primeras páginas. Aquí esta algo de la información que viene con el programa:
Cita: Advanced eBook Processor, or simply AEBPR, is a program to decrypt eBooks in Acrobat eBook Reader format (PDF files with EBX security handler), as well as Adobe Acrobat PDF files protected using standard security method, WebBuy technology, or any other Acrobat security plug-in (like FileOpen, SoftLock etc) by converting them into plain PDF files -- without any protection and restrictions. Decrypted file can be opened in any PDF viewer (e.g. Adobe Acrobat Reader) with edit, copy, print, annotate functions enabled. All versions of Adobe Acrobat are supported. Can also decrypt eBook Pro (*.EBK) files, extracting all html pages and images from them.
También hay que recordar que la modificación de ciertos contenidos viola las leyes de copyright.