Convert pictures and PDFs

How do you turn photographs into a PDF?

Drop the pictures onto the tool above and press Save PDF. Each photograph gets its own A4 page with the picture fitted inside it, in the order you added them. That last part matters more than it sounds: a photograph straight off a phone is whatever shape the camera sensor is, and a PDF built the lazy way comes out with pages of five different sizes that no printer will handle sensibly.

The commonest reason a teacher wants this is evidence. Twelve photographs of work on a table become one document that can be attached to an email, dropped into a folder, or printed as a record — instead of twelve files that arrive in a random order.

How do you get a PDF page out as a picture?

Drop the PDF in instead and the tool switches round: every page is drawn as a JPG or PNG at 150 dpi, and you save them. A one-page PDF gives you one picture; anything longer comes back as a ZIP, which your computer unpacks with a double click.

This is the answer to the most annoying small problem in teaching — the worksheet you want to put on a slide, which will only paste as a stubborn full-page block. As a picture it drops in, resizes and sits where you want it.

Why will my iPhone photos not open on the school computer?

Because iPhones save photographs as HEIC, a format Apple uses and most school Windows machines cannot read. The picture is fine; the computer simply has no idea what it is looking at. Converting it to JPG or PNG solves it permanently, and this tool decodes HEIC before doing anything else, so you can drop iPhone photos in without thinking about it.

If you would rather stop the problem at source, the iPhone can be told to take photographs in the compatible format: Settings, then Camera, then Formats, then Most Compatible. Worth doing on a school iPad before anyone else uses it.

JPG or PNG — which should I pick?

JPG for anything photographic and PNG for anything with lines and text in it. A photograph as a PNG is several times bigger for no visible gain; a diagram as a JPG picks up soft grey fuzz around every line, which shows badly on a whiteboard.

What it is	Pick
Photographs of work, of a display, of a trip	JPG — much smaller files, and nothing is lost that anyone can see.
A worksheet, a diagram, a page of text	PNG — every line stays crisp, which matters when it is going on a screen at the front of a room.
Going into a document or an email	JPG, unless the fuzz is obvious. Size is what will stop it sending.

Does converting lose quality?

A little, and where it goes matters. Turning pictures into a PDF re-saves them as high-quality JPG, which is invisible on a photograph. Turning PDF pages into pictures redraws them at 150 dpi, which is fine on screen and fine printed at the same size, but not enough to blow up onto a wall.

If the plan is to blow it up onto a wall, the poster tool takes your original at full resolution rather than a converted picture, and will look considerably better for it.

Converting, or compressing?

They get confused because both make files smaller. Converting changes what kind of file it is — pictures to a PDF, or a PDF to pictures. Compressing keeps it a PDF and squeezes what is inside. If the problem is that something will not open, convert it. If the problem is that it will not send, compress it.