Answered
Any way to combine or add tagged pdfs and not lose ordered structure?
I've created a 96 pg tagged pdf and cleaned it up in Acrobat X. Then I needed to replace the first 2 pages. I created 2 separate tagged pdfs and reordered then. Next I combined pdfs. The new binder came in with Parts. I dragged out the Articles and Stories, but all tags, which I'd reordered in the 96 pg pdf were partially out of order and will require quite a bit of reordering.
Yes and no. When a Tagged PDF is used via replace page(s), insert page(s) and such this PDF's structure tree will be appended to the end of the existing structure tree.
When manually assembling many PDFs into one you'd open the first (say Chapter_1.pdf) then insert the next in sequence behind the last page of this "first in content" PDF. Continue down the line.
Similarly, using the combine feature you'd need the files to be ordered first to last (top down) in the combine dialog. In the Options dialog you might play with having the accessibility choice unticked. The PDFs to be combined already have their structure. Otherwise the software will add.
As to "Part", it is a higher level Grouping element. Remember, grouping elements group other elements into sequences or hierarchies but hold no content directly and have no direct effect on layout.
So, "Part" makes sense (particularly if Combine's accessiblilty option is "on"). "Part" is the second highest BLSE Grouping element (after "Document").
.
--| Document is the whole enchilda.
--| Part groups Articles or Sections.
--| Article is for those self-contained runs of text (the essay, the newsletter article, etc.).
(Article is not to contain other "Article" grouping elements as a "child" element.)
--| Section groups related content (many paragraphs of content within text flow). Section can/does have "Section" repeated as a child (e.g., a chapter's sub-sections).
--| Division (a generic block-level grouping element) for rounding up stuff (sort of akin the HTML's "Div").
There are others but the above are seen rather often.
The above list denotes the "sequence" of the BLSE Grouping elements. "Document" is never a child. "Part" can be a child of "Document" but not of Article or Section.
By the way, provided the structure tree within a "Part" tag is ok you'd not have to do anything with "Part".
Pull in the PDF at the link below; it is Adobe's ISO authorized release of ISO 32000-1. Start with Section 14.7. As the information gels you'll find yourself meandering through the grooves of the other sections.
The ISO Standard is on its way to "dash 2" and a freebie may not be available once it is published.
http://wwwimages.adobe.com/www.adobe.com/content/dam/Adobe/en/devnet/pdf/pdfs/PDF32000_2008.pdf
.
Be well...