Will the Word file actually be editable?
Yes. The output is real WordprocessingML: paragraphs, runs, heading styles, numbering definitions and tables. Nothing is dropped in as an image of the page, so you can click into any sentence and retype it.
Does it open in Google Docs and LibreOffice too?
It does. The package is written to the OOXML spec rather than to any one application, and every part of it is checked for well-formed XML before you get it, which is what stops Word showing its unreadable-content repair prompt.
Is my PDF uploaded anywhere?
No. Reading the PDF, rebuilding the document and writing the .docx all happen in your browser. The file never leaves your device, and neither does the Word file that comes out of it.
My PDF is password-protected. Can I convert it?
Not directly - an encrypted PDF has no readable text until it is unlocked. Run it through the Remove PDF Password tool first if you know the password, then convert the unlocked copy.
How close to perfect is the result?
Text, headings, lists, tables, images, links and page geometry come across reliably on documents that carry a text layer. Very dense forms, heavily nested tables and pages that mix several layouts at once may still want a few minutes of tidying. Nobody converts a PDF perfectly every time, and anyone who says otherwise has not tried enough PDFs.