PDF, PNG or JPG: which one should you actually send?

These get treated as interchangeable ways of sending a picture of something. They are not, and the differences show up at exactly the wrong moment — when a document is rejected, or a scan is unreadable.

The distinction that matters is not quality. It is what each format is built to store: instructions, exact pixels, or approximate pixels.

PDF stores instructions

A PDF page is a description — draw this text, in this font, at this position. Nothing has a resolution, so a page can be displayed at any size and printed at any size without degrading. It holds multiple pages, keeps text selectable and searchable, and looks identical everywhere.

This is why every organisation asks for PDF. It is the only one of the three that is a document rather than a picture.

PNG stores exact pixels

PNG is lossless: every pixel is preserved precisely, and saving it repeatedly never degrades it. That makes it right for screenshots, diagrams, logos and line art — anything with hard edges. It also supports transparency, which neither of the others does.

The cost is size. A full page as PNG is large, because nothing is being approximated away.

JPG stores approximate pixels

JPG achieves small files by discarding detail the eye is least likely to miss — and it concentrates that discarding at sharp edges, because photographs have few of them. Text is nothing but sharp edges, which is why words saved as JPG pick up a faint grey halo that worsens every time the file is re-saved.

Rule of thumb: photographs as JPG, anything with text or hard edges as PNG, anything anyone official will read as PDF.

The choices people actually get wrong

• Sending a JPG of a document to an organisation. It will often be rejected, and if accepted it cannot be searched.
• Saving a screenshot as JPG. Interface text is the worst possible content for JPG compression.
• Sending a PNG of a photograph. It will be several times larger than the JPG for no visible benefit.
• Re-saving a JPG repeatedly. Each pass loses a little more, and it never comes back.

Converting between them

Going from images to a document is the common direction: JPG to PDF and PNG to PDF place your images into pages without recompressing them.

The other direction depends on what is on the page. PDF to PNG for pages of text, tables or diagrams; PDF to JPG for pages that are mostly photographic. There is more on resolution in the guide to converting without losing quality.

Whichever direction you are going, resolution is the setting that decides whether the result holds up: 150 DPI for screen, 300 DPI for print. Most converters quietly default to 72, which is why so much converted output looks soft.

Common questions

Which format should I send to an employer or government office?

PDF, essentially always. It is the only one treated as a document, and many upload forms accept nothing else.

Is PNG always better quality than JPG?

PNG is always more faithful, because it discards nothing. For a photograph that fidelity is invisible and the file is several times larger, so 'better' depends on what is in the image.

Does converting a PDF to an image lose the text?

Yes. The page becomes pixels that look like letters, and nothing can be selected or searched afterwards. Keep the PDF if the text matters.