It is the most requested conversion and also the most misunderstood, so it's worth being clear about what to expect. PizzaPDF reads the words in the PDF and their positions on the page, rebuilds the lines, joins them into paragraphs where the line spacing stays regular and recognises headings by font size. What you get is a clean .docx, with selectable, editable text.
What you don't get is a faithful copy of the layout: columns, tables, images and original fonts are not rebuilt. On documents with a complex layout the order of the text can come out muddled. This isn't a limit of this particular site: a perfect PDF-to-Word conversion doesn't exist, because a PDF describes where to draw marks on the page, not how the document is structured.
On a report, a letter or a contract the result is excellent. On a three-column leaflet, much less so. If the PDF is a scan — that is, pictures of pages — nothing comes out, and the tool tells you so instead of giving you an empty file.