DOC vs DOCX — does it matter which one you get?
For nearly all practical purposes, no. .doc was Word's binary format up through Word 2003; .docx replaced it starting with Word 2007 and has been the default ever since. Any word processor released in the last decade and a half opens .docx natively, including free tools like Google Docs and LibreOffice.
PrivaPDF converts your PDF to .docx rather than the legacy .doc format, since .docx is smaller, more robust, and universally supported by anything you're likely to open it in. If a specific workflow genuinely requires the older binary .doc format (uncommon outside of legacy enterprise systems), most word processors can re-save a .docx as .doc in a couple of clicks after conversion.