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Participating Frequently
September 11, 2022
Question

PAC unhandled exception: MCID 1 already present.

  • September 11, 2022
  • 3 replies
  • 9218 views

I received this pop-up when running a PDF through PAC. I don't know what it means, so I don't know how to fix it. I'm not clear on what an MCID is or how it functions, so I need help understanding the pop-up and also resolving whatever is causing the pop-up. Note that the PDF otherwise passes PAC and Acrobat's Checker.

3 replies

New Participant
November 18, 2025

Hi, I found a laborious but working solution. It took time, but less than redoing the document. Just to note: my document is not a compilation of various documents, and it broke down at some  point during remediation. (Originally created in InDesign.)

 

Here is what I did: I sliced up a backup copy, to find out which page causes the problem. (Delete half the pages, save, check with PAC. If error persists, delete the half of the rest... If result is clean, work with the other half...) In the end I was left with one page.

 

I could have replaced that page with a page from a previous, uncorrupted save. But instead, I tried to find the problematic content element on the page. I did it by working with a one-page copy, removing content elements. The error was caused by an image that was spreading through 2 pages. I tagged the part that was on this page. (Tricky method: Move the element out from its container in the Content panel, then delete the container. Then select and tag as a figure with the Reading Order tool.) Then I turned it into an artifact. 

 

I am not a hundred percent sure that it always works, but should be a solution for various cases.

ls_rbls
Community Expert
September 12, 2022

++Adding to the discussion,

 

Which PAC version and operating system are you on?

 

 

It would be helpful if you also share a screenshot of the PDF/UA check after you click on the start button.

 

When you run the PAC console post the screenshot with emphasis on the elements that currently show a yellow warning triangle amd any other element identified with a red X for  partially accessible elements.

 

That said, ca you confirm if one of those warnings is related to the Font type used?

Participating Frequently
September 12, 2022

As I mentioned, this document otherwise passes PAC (2021). There are no errors, only this pop-up. 

hammer0909
Community Expert
April 12, 2025

I haven't found a good solution other than "try again". Typically I encounter this error when I combine several files into one. The MCID is burried as an attribute of a tag that is painfully time consuming to find. I can't tell you what actually causes it. But usually if I combine them again, I can get a good file without the error. I recommend using the Organize Pages tool to combine files. I've had the best luck with that method.


Recently, a few products have emerged on the market that are giving us the ability to deal with duplicate MCID errors. I'd take a look at GrackleDocs and PDFix.

hammer0909
Community Expert
September 11, 2022

Is this a PDF that you created by combining multiple PDF files into one? 

Participating Frequently
September 12, 2022

Yes. A client combined it and we couldn't change that.

Participating Frequently
September 12, 2022

Chad: This started as a series of combined Word documents (not PDFs--I reread your post). We converted and added redaction boxes where the client told us to do so. There are a series of 18 of these, ranging from maybe 10 pages to ~100. Only 3 of the 18 have this pop-up, and it's not always "MCID 1." Sometimes it's "MCID 0" or "MCID 2."