PDF vs Word (DOCX) vs Images vs PDF/A: Which Format Should You Use?

"Just send it as a PDF" is common advice, but it is not always right. PDF, Word (DOCX), image formats such as JPG and PNG, and the archival variant PDF/A each solve a different problem. Pick the wrong one and you get a document nobody can edit, a layout that falls apart on someone else's computer, or a file that will not open correctly in ten years. This guide explains what each format is actually for and gives you a simple way to choose.

The one distinction that explains everything

Almost every format decision comes down to a single question: do you want the document to be editable, or fixed?

• Editable formats (like DOCX) store your content as flowing, changeable text and layout. They are made to be worked on.
• Fixed formats (like PDF and images) store a finished appearance. They are made to be shared and viewed exactly as-is.

Get that right and the rest follows.

Word / DOCX — for documents you are still working on

Microsoft Word's DOCX is a living document format. Text reflows, styles cascade, tracked changes and comments support collaboration, and anyone with a compatible editor can rewrite it.

Use DOCX when:

• You are drafting or collaborating and the content will keep changing.
• Someone needs to edit or reuse the text.
• You want features like track changes, comments, or mail merge.

Its weaknesses are the flip side of its strengths. The layout can shift between computers depending on installed fonts and Word versions, and because it is editable, it is the wrong format for anything final, official, or signed. When a DOCX is done, it is usually converted to PDF for sending.

PDF — for finished documents you share

PDF is the fixed-layout standard. It embeds its fonts and freezes the position of everything on the page, so it looks the same on every device and printer (see how PDFs actually work). It supports selectable text, links, forms, and signatures.

Use PDF when:

• The document is final and should look identical for every recipient.
• You are sending an invoice, contract, résumé, report, or form for signing.
• You need to combine several things — pages, scans, images — into one tidy file.
• You want it to print predictably.

PDF is deliberately hard to edit, which is a feature for finished documents and a limitation while you are still writing. When you do need to change a PDF, you merge, split, reorganize pages, or sign it rather than retyping.

Images (JPG / PNG) — for pictures, not documents

It is tempting to screenshot a page and send the image, but image formats are built for pictures, not documents.

• JPG (JPEG) compresses photographs efficiently but is lossy — it discards detail, and text edges become fuzzy. Every re-save degrades it further.
• PNG is lossless and keeps text and sharp edges crisp, and it supports transparency — better for screenshots, logos, and diagrams, at a larger file size.

Use an image when the thing genuinely is an image (a photo, a screenshot, a graphic), or when you must post to a platform that only accepts images. Avoid images for multi-page documents: they are not searchable, they do not preserve real text, they are awkward to print at the right size, and several images are clumsier to send than one PDF.

When you do need to cross the line, convert deliberately: turn images into a single PDF (great for combining photos of receipts or JPGs into one file), or export PDF pages to PNG or JPG when a platform demands an image.

PDF/A — for long-term archiving

PDF/A is a stricter archival subset of PDF, designed so a document will still open and look correct decades from now. It enforces the rules that make that possible: all fonts must be embedded, no external dependencies, no encryption, and no features (like JavaScript or linked media) that might break over time.

Use PDF/A when:

• You are archiving records, or a court, government body, library, or compliance process requires it.
• The document must remain self-contained and reliably reproducible for many years.

For everyday sharing you do not need it — a normal PDF is simpler. We cover the trade-offs in PDF/A vs PDF: which format do you need.

Side-by-side comparison

A quick decision guide

• Still writing it? Keep it in DOCX until it is finished.
• Sending it to be read, printed, or signed? Export to PDF.
• Is it literally a photo or screenshot? Use JPG (photos) or PNG (screenshots, graphics) — but if it is more than one, wrap them in a PDF.
• Does it need to survive for years, or does a rule require it? Save as PDF/A.
• Got the wrong format? Convert it: Word to PDF, PDF to Word, images to PDF, or PDF to images.

What about Google Docs, Pages, and ODT?

DOCX is not the only editable format. Google Docs stores documents in the cloud and exports to DOCX or PDF; Apple Pages is the Mac equivalent; and ODT (OpenDocument Text) is the open-standard format used by LibreOffice. For the purpose of choosing a format, they all play the same role as DOCX — editable, reflowing formats for work in progress — and the same advice applies: keep working in them while drafting, then export to PDF when the document is final and needs to look the same for everyone. There are also lightweight text formats worth knowing: plain text (.txt) holds characters with no formatting, Rich Text Format (.rtf) adds basic styling in a widely compatible way, and Markdown (.md) writes formatting as simple symbols. All three are great for writing and portability, but none of them fix layout the way a PDF does — so when appearance and printing matter, they too get exported to PDF.

Format by scenario

• A résumé: write it in Word, send it as PDF so the layout never breaks on a recruiter's machine.
• An invoice: always PDF — it is a final financial record that should look identical and be easy to archive.
• A photo of a receipt: it is already an image; if you have several, combine them into one PDF rather than attaching a dozen JPGs.
• A form to be filled and signed: PDF, ideally with real form fields, then flattened after signing.
• A document to archive for a decade: PDF/A, so it is guaranteed to open and reproduce correctly.
• A draft going back and forth with edits: keep it in DOCX or Google Docs until everyone agrees, then freeze it as PDF.

A note on converting quality

Every conversion has a catch worth knowing. Word-to-PDF is clean and reliable. PDF-to-Word is an approximation — the layout is rebuilt from positioned text, so complex formatting may shift and you should always proofread the result. Image-to-PDF is lossless (the picture is embedded as-is), but PDF-to-image is a re-rendering, so choose a high enough resolution for your purpose. And turning a scan into editable text needs OCR, which is a best-effort reading of an image, not magic. When in doubt, keep the original file so you always have a clean source to convert again — and remember that file size is usually driven by images, not by the format itself, so the real fix for a huge file is compression, not a format change.

Keep an editable master, share a PDF copy

A habit that sidesteps most format headaches: keep your working document in an editable format (DOCX or Google Docs) as the master, and generate a PDF copy whenever you need to send, print, or archive. The master stays easy to update; the PDF is the frozen snapshot others receive. When something changes, edit the master and re-export — never try to edit the PDF and then reconcile two diverging versions. Name the files so the two never get confused (a dated master and a clearly labeled PDF), and you will always know which one to edit. It also means you never have to reverse-engineer a finished PDF back into an editable document, which — as noted above — is only ever an approximation. This "edit the source, publish the PDF" workflow is how most professional documents are actually maintained.

Key takeaways

• The core choice is editable (DOCX) vs fixed (PDF/images).
• Use DOCX while drafting, PDF once it is final, and images only for actual pictures.
• Prefer PNG for screenshots and line art, JPG for photos, and never send a multi-page document as loose images — combine them into a PDF.
• Reach for PDF/A only when you need guaranteed long-term reproduction or a rule requires it.
• Converting between formats is quick and can be done entirely in your browser without uploading your files.