The text box problem
It is the most common complaint about PDF-to-Word conversion, and it sounds trivial until you meet it. The file opens. It looks right. Then you try to change a sentence and the whole thing falls apart, the text will not reflow, the cursor jumps somewhere unexpected, and deleting a line leaves a hole.
What you have is not a document. It is a page with a box drawn on it for every line of the original, each box containing that line of text and pinned to the coordinate it occupied in the PDF.
Why converters do it
Because it is the path of least resistance, and because it makes the "preserves your formatting perfectly" claim technically true.
A PDF has no paragraphs. It has instructions of the form "draw these characters at 214, 588 in 11pt Times". To reproduce the page exactly, a converter only needs to place each of those fragments in a box at the same position. No interpretation required, and the output is a pixel-accurate match.
To produce something editable, the converter has to work out what the fragments mean: which lines belong to the same paragraph, which are headings, which are list items, and what order any of it should be read in. That is inference, it can be wrong, and it produces a document that no longer matches the original exactly. Most converters decline the problem.
The three inferences that make a document editable
Reading order. A PDF records no order that means anything. On a two-column page the columns share their baselines, so a converter reading across the page interleaves them, a line of the left column, then a line of the right, and produces text nobody can use. The columns have to be found geometrically first.
Paragraph reassembly. This is the one that matters most. A PDF breaks a line wherever the text ran out of column, and those breaks carry no meaning. If they are preserved, every line becomes its own paragraph and the document behaves like a stack of index cards. Joining them back up, while keeping the breaks that are meaningful, between real paragraphs and around list items, is what makes the file behave like a Word document.
The tool above reports how many lines it joined, so the work is visible rather than asserted.
Heading detection. Inferred from font size relative to the body text, with two sanity checks: a heading is short, and it does not end in a full stop. Without those, the first line of any paragraph in a slightly larger face becomes a heading. The result is written as a real Word heading style, so the navigation pane and table of contents work.
What you cannot have
Being plain about the trade, because the marketing around this is not.
You cannot have an exact visual match and an editable document. They are opposites. An exact match is positioned boxes; editable is flowing text. Any converter promising both is giving you the first and calling it the second.
So: images are left out (with a note where each page had them), page numbers and running headers are dropped, and precise spacing is not reproduced. What you get is the content, in the right order, with its structure intact, paragraphs, headings, lists and tables, in a file that behaves normally when you type in it. If what you needed was the layout, you did not want Word, you wanted the PDF.
After converting
Read the preview above against the original before downloading. Ten seconds of checking catches the cases inference gets wrong, and the clean-up guide covers the five steps that turn a rough conversion into a finished document in about ten minutes.
If you are converting to feed the document to an AI tool rather than to edit it, the Markdown converter is the better target, it keeps the same structure at a fraction of the token cost.