Just curious, what process did you use to "export" from pdf?

Converted documents are always painful to deal with, even ones that are converted from Word to another format and then back. They will generally have an incredible number of continuous section breaks, among other things. This is because most other programs use margin changes where Word would use indents. When they are converted to Word, they are converted with margin changes. These days, conversion software does a passable job of creating documents that look the same. The underlying structure, though, is often radically different.

I suspect in your document screen shot of Section 8 there is a margin change at each paragraph. Each margin change, in Word, requires a Section break (new section), usually continous. Each Section in Word will contain three headers and three footers (even if never used) and can contain pagination instructions. The header/footer shown would be from the first section on the page. I can reproduce the section numbering "jump" with continuous section breaks on a page.

Sections / Headers and Footers in Microsoft Word 2007-2013