Quick answer: use Word (.docx) while a document is still being written or edited, and PDF once it's finished and needs to look the same for everyone who opens it. Word is for changing content; PDF is for sharing, printing and sending documents that shouldn't be casually altered.
Need to switch? You can convert a PDF to Word to edit it, and turn a Word document into a PDF when you're done — both free, in your browser.
What is the difference between PDF and Word?
Word (.docx) is built for writing and editing. It stores a document as flowing, structured content — paragraphs, styles, headings — that's meant to keep changing as people work on it. Change the page size or add a sentence and everything after it reflows.
PDF is built for presenting and sharing a finished result. It fixes every element in place and usually embeds the fonts it uses, so the document looks identical on any screen or printer, whatever software the recipient has. That reliability is also why PDFs resist editing — they were never meant to change.
Both are open, widely supported formats. PDF was created by Adobe in the early 1990s and is now an international standard (ISO 32000), which is why every browser and phone can open one without extra software. The .docx format arrived with Word 2007 and is also standardised, so Google Docs, Apple Pages and LibreOffice all read and write it.
| Word (.docx) | ||
|---|---|---|
| Best for | Drafting, editing, collaborating | Final, shareable, printable documents |
| Looks the same everywhere? | Can shift with fonts and software | Identical on every device |
| What you need to open it | Word, Google Docs, Pages or LibreOffice | Any browser or phone — viewers are built in |
| Easy to edit? | Yes, by design | Not without converting or paid software |
| Comments & track changes | Full support | Annotations and highlights only |
| Contracts and signed documents | Easy to alter, deliberately or by accident | Harder to alter; supports digital signatures |
| Forms | Possible, but fiddly for recipients | Fillable forms work in most viewers |
| Long-term archiving | Can render differently in future software | PDF/A is a version designed for archiving |
| Typical file size | Small for text-heavy documents | Can be larger with embedded fonts and images |
When should you use Word?
- You're still drafting, and the content will keep changing
- Several people need to edit, comment on or track changes in the same document
- You need Word's tools — styles, templates, mail merge, a table of contents that updates itself
- Someone has asked for an editable file, such as an editor, a recruiter or a colleague who'll build on it
When should you use PDF?
- The document is finished and you want it to look identical for every recipient
- You're sending something that shouldn't be casually altered — an invoice, a signed contract, a quote
- You need it to print predictably, page for page
- The recipient may not have Word, or will read it on a phone
A useful habit: keep the Word file as your working copy, and send a PDF made from it. That way you always have an editable original and a fixed version for sharing.
What about .doc, Google Docs and other formats?
.doc is the older Word format used up to Word 2003. Modern Word still opens it, but .docx is the default now and is what you should use unless someone specifically asks for .doc. Google Docs files live online in your Google account; you can download them as .docx or PDF from File → Download. .odt is LibreOffice's own format, and Word can open that too.
How to convert between PDF and Word
Word to PDF is usually the last step before sharing. In Word, use File → Save As and choose PDF; in Google Docs, File → Download → PDF Document; in Pages, File → Export To → PDF. No Word installed? Altto's Word to PDF tool does it in your browser — our guide on converting Word to PDF covers every method.
PDF to Word is the common case going backwards: you've been sent a PDF — an old contract, a form, a report — and there's no Word original, but you need to change the text. A converter rebuilds the PDF as an editable .docx. Altto's converter keeps text, tables, images and column layouts, runs OCR automatically on scanned pages, and does it all on your device. See how to turn a PDF into a Word document for six ways to do it.
Can you edit a PDF without converting it?
For small changes, sometimes. Free viewers such as Preview on a Mac and the PDF viewer built into Microsoft Edge let you highlight, add text and fill in forms, and Preview can add a signature. Changing the existing text itself generally needs paid software such as Adobe Acrobat. For anything more than a few words, converting to Word, editing, and saving back to PDF is usually the easiest route.
Common questions
Is PDF or Word better?
Should I send my CV as a PDF or a Word document?
Is a PDF more secure than a Word document?
Can I turn a PDF back into an editable Word document?
Why does a PDF look the same on every device?
What's the difference between .doc and .docx?
Have a PDF that needs editing?
Convert it to an editable Word document in your browser — free, and nothing is uploaded.
Sources
Where the format facts in this guide come from:
- ISO — ISO 32000-2:2020, Portable document format – PDF 2.0 (PDF as an international standard)
- Ecma International — ECMA-376, Office Open XML file formats (the standard behind .docx, also published as ISO/IEC 29500)