PDF Packages were introduced in Acrobat 8.0 and they themselves were an extension to simple file attachments in a PDF file. With PDF Packages, you could combine multiple PDF files into a single “Package” with each file remaining a discrete entity with it’s own security settings but you could also combine Dynamic XFA Forms and static PDF Forms (Acroforms). What distinguished PDF Packages from ZIP files is that you could add descriptive text and metadata in context and you’d get a little thumbnail to help you find the specific files you wanted across the whole set.

One of the more interesting features of Adobe Acrobat is the ability to review and markup documents using electronic versions of common tools used to mark up paper documents. Acrobat gives you a highlighter, a sticky note tool, even a paperclip to attach additional documents or files. These are stored as annotation on top of the PDF pages. The Datalogics PDF Java Toolkit allows developers to create, modify, extract and manage these annotations in a way that is completely interoperable with Adobe Acrobat.