I need to allow a document to have multiple people sign and attach things to it. For instance I am looking to create a form where someone asks a question and can attach a document. They will then sign a digital signature block that will make their question read only. after sending the form for an answer they responder will then be able to fill out the "answer" field and add an attachment if necessary. this will ensure that the question nor the answer are modified but I still need the ability to add attachments by the "responder" after the "requestor" has already signed the document. What is a PDF Portfolio?