I'm not exactly sure what you're trying to do. But in thinking of documents the only hierarchy of which I am aware are things like an outline, where you have sections, sub-sections, etc.
Assembler will not format the pages of your document, although you could add a header which identifes that part of the outline.
And further you could add bookmarks to the PDF which identifies it, and then you would have to "roll up" the assembly.
Here's a very simple example:
<?xml version="1.0"?>
<DDX xmlns="http://ns.adobe.com/DDX/1.0/"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
>
<PDF result="Chap1" return="false">
<PDF source="Section1-1" bookmarkTitle="Section 1-1" />
<PDF source="Section1-2" bookmarkTitle="Section 1-2" />
</PDF>
<PDF result="Chap2" return="false">
<PDF source="Section2-1" bookmarkTitle="Section 2-1" />
<PDF source="Section2-2" bookmarkTitle="Section 2-2" />
</PDF>
<PDF result="Chap3" return="false">
<PDF source="Section3-1" bookmarkTitle="Section 3-1" />
<PDF source="Section3-2" bookmarkTitle="Section 3-2" />
</PDF>
<PDF result="Report.pdf">
<PDF source="Cover" bookmarkTitle="Cover" includeInTOC="true"/>
<TableOfContents maxBookmarkLevel="infinite"/>
<PDF source="Chap1" bookmarkTitle="Chapter 1" />
<PDF source="Chap2" bookmarkTitle="Chapter 2" />
<PDF source="Chap3" bookmarkTitle="Chapter 3" />
<PDF source="Summary" bookmarkTitle="Summary" />
</PDF>
</DDX>
The PDF document sources required to be provided in the inputs map would be
Section1-1
Section1-2
Section2-1
Section2-2
Section3-1
Section3-2
Cover
Summary
I hope this helps.
