Different formats for different jobs
Word (DOC/DOCX) is an editing format. It stores your content in a flexible structure that reflows as you change margins, fonts, or page size.
PDF is a presentation format. It freezes your document so it looks identical everywhere, which is why it is the default for anything you send to be reviewed, signed, or printed.
Editing and collaboration
Word excels at collaboration: tracked changes, comments, real-time co-editing in Microsoft 365, and easy style updates.
PDFs can be annotated and form-filled, but deep editing usually requires converting back to Word, editing, and re-exporting.
A simple rule of thumb
Author and collaborate in Word. Share, sign, and archive in PDF. When you receive a PDF that needs editing, convert it back to Word, make your changes, then re-export.
Frequently asked questions
You can annotate, sign, and fill forms in most PDF viewers, but full text and layout editing usually requires either a PDF editor or conversion back to Word.