function PageObjectMarkedContentID(Index: Integer): Integer;
| Index | Integer. Zero-based index of the page object. |
| Result | Integer. The /MCID value of the object, or -1 when the object is not part of any marked-content sequence. |
In a tagged PDF, structure elements refer to page content through marked-content identifiers. Given an object, this returns the identifier a structure element would use to point at it, which is what a reading-order or accessibility tool needs to join the two halves
A result of -1 means untagged content, a normal state in an untagged document and a finding worth reporting in one that claims PDF/UA conformance
Use IsTagged to tell whether the document declares a structure tree at all