@johnmann04 Unfortunately, this approach will not give the desired result. The text paginating algorithm in MS Word is not always obvious and predictable; adding text to a paragraph may cause the paragraph to get moved to the previous page. This is exactly what happens in your document:
LayoutCollector correctly identifies that the problematic paragraph is on page 14, however, when adding text to it, the paragraph is moved by MS Word to page 13.
You can try to get workaround this problem in various ways. For example, add text to a separate line initiated by BreakType.LineBreak, so that the logic of the rest of the code is not changed.
foreach (Paragraph paragraph in paragraphs)
if (collector.GetEndPageIndex(paragraph) != pageIndex) continue;