Document attached to a process is not viewable via process and task form to Business Central users in BPMS 6

Issue

• The requirement is to attach a document to a process form, so that user should be able to view that document at subsequent stages (user tasks) within the process. It only needs to be visible during the lifetime of the process instance. This should be done in Business Central, with no custom code involved in the picture. How to achieve that goal?
• Also, how to make the process attachment visible to Task forms so that it is not only visible but also updated?
• Even after following the instructions in the user guide for attaching a document to a form, where a user has created a process variable called doc of type org.jbpm.document.Document. Then, in the process form, if the user adds a field of type Document, and mapped its Output Binding Expression to doc, it should be expected that whatever document is uploaded to that field to be mapped to the process variable doc. It is not happening like the way it is expected.
• After running the process user can upload a document using the form field without any problem, but on submission of the form, the document is nowhere found throughout the process lifecycle. It is expected that the document should be viewable in the process instance's Documents tab, but there's nothing there. Is there anything missing?