Converting PDF to DOCX gives you a Word file whose text you can change, instead of a fixed page you can only read. Because a PDF records where characters sit rather than how paragraphs are built, the converter has to reconstruct the structure, so plain one-column documents come through cleanly and complex layouts usually need some tidying.
Transfers use HTTPS, and files converted on the free tier are deleted within 24 hours, so the result is not a long-term archive. Quality depends on the source file, so open the DOCX file once before you share it.
FromPDFLossless
PDF (Portable Document Format)
A page description format standardised as ISO 32000. It stores glyphs, images and vector shapes at fixed coordinates on each page, with no built-in notion of paragraphs, columns or table cells unless the file was specifically tagged with structure.
ToDOCXLossless
DOCX (Office Open XML Document)
Microsoft Word's Office Open XML document format, a zipped set of XML files. Content is stored as paragraphs, runs, tables and styles that reflow when edited, and it opens in Word, Google Docs, LibreOffice Writer and Apple Pages.