PAC unhandled exception: MCID 1 already present.

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.

++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?

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