When to send a PDF
For anything official — contracts, applications, invoices, CVs — send a PDF. It opens the same on every device, keeps multiple pages in order, looks professional, and can't be edited by accident. Most forms and portals expect a PDF, not a photo.
When an image is fine
For a quick, casual share — a screenshot, a photo of a receipt for a friend, or something going into a chat — an image is faster and perfectly fine. Images are also the right choice when the visual itself is the point, like a photo you want someone to see full-screen.
Converting between them
The good news: you can switch either way in seconds. Turn photos of documents into one tidy PDF when something official is needed, or convert PDF pages into images when you want to post or preview them. Both run free in your browser, so you're never stuck with the wrong format.