1

Working with a PDF assembled from multiple PDFs the PDF Accessibity Checker (PAC) throws an error "PAC Unhandled Exception MCID 1 already present."

Is there any way to see and/or fix this issue from within Acrobat or ?? Is the MCID visible within an element's Tag?

What are MCIDs used for and does having duplicate MCIDs cause accessibility issues??

raeben
  • 17
  • 2
  • 2
    "Is there any way to see and/or fix this issue from within Acrobat or ??" Acrobat Pro has a nice Tagged PDF explorer. "Is the MCID visible within an element's Tag?" Not sure what you mean by this. "What are MCIDs used for and does having duplicate MCIDs cause accessibility issues?" They are used to map Marked Content in the Page Content Stream with the Logical Structure tree in the PDF objects. And yes, duplicates would probably cause issues. – Ryan Sep 12 '22 at 20:40
  • Thanks for your response. I’m familiar working with tags in Acrobat but these are long documents and no idea where the problem is and how to see it in the tags. Are these IDs related to the autogenerated IDs shown in the Acrobat Tag Properties or are they something else again? Have tried AxesPDF tools: rebuild structure, repair parent keys, remove corrupt elements and remove broken MCRs (this last generates an error). Maybe extracting all the pages and checking each would isolate the problem? – raeben Sep 14 '22 at 14:20
  • 1
    Although I still don't really understand what an MCID is -- it does not seem to be the ID visible in the Tag's File Properties because deleting them seemed to have no effect. I was able to resolve the problem by breaking the file down into successively smaller sections (20 pages then 10 pages, etc.) and testing each one. One page was causing this error so I deleted the tags on that page and retagged it, inserting it in the larger file. Whole file seems to be OK now. No MCID error. – raeben Sep 14 '22 at 16:37

1 Answers1

0

Not an answer, but "MCID n already present" -error appears in PAC (and in axesPDF which contains PAC) as soon as one edits the existing content in a tagged PDF so that some object is somehow rebuilt. Seemingly the tagging is something extra on the basic PDF structure and PDF editing handles tags only with the left hand.

An useful thing to do is to open Acrobat's Content panel which shows the objects, their layering order and tag containers where the objects are placed to.

PAC "MCID n already present" -errors stopped to appear after my PDF edits when I moved possibly soon to be affected objects out of the tag containers in the Content panel and deleted those containers. Then I did my edits, typically moved or changed some text and retagged it.

A person who really knows what Acrobat will do when one make edits maybe could tell which objects could stay in the tag container and move out only those which will be affected by the edits. And then move them back after editing. Moving all content out of the tag container and deleting the empty container, editing and finally retagging in the usual way after the edits has anyway worked.

Unaremediator
  • 1
  • 1