Convert images to PDF

Why a PDF and not a folder of images

Because almost every place that asks for a document will take a PDF and will not take a zip of photos. A visa application, a claim form, a university portal, a landlord, a tax office: one file, in order, that opens the same way on every machine. That is the whole job, and the parts that go wrong are the page size and the order.

Fit, or a paper size

Fit makes each page exactly the shape of its image. Nothing is cropped, nothing is padded, and there are no white bands — which is what you want for photographs, screenshots and anything that will be read on a screen.

A4, Letter, Legal, A3 or A5 puts each image on a real paper page, scaled to fit inside it and centred. Choose one of these whenever the file might be printed, or when a portal specifies a paper size. The letterboxing that appears around an image whose shape does not match the paper is not a flaw — it is the page being the size you asked for.

Auto orientation turns each page to match its image, so a mixed set of portrait and landscape photos does not leave half of them small and sideways. Fix it to portrait or landscape when every page must be the same way up, which some print shops and binding services require.

Margins

Zero by default, because a scan of a document already has its own white edge and adding more shrinks the content for no reason. A margin is worth setting when the pages will be printed and punched or bound, where the inner edge disappears into the binding.

The order is the filename order

Pages come out in the order the files are listed, and you can drag them into place before converting. This is the one to check before you download, because it is invisible in a folder view and obvious in a finished document.

The common trap is that phone cameras and scanners name files IMG_1 through IMG_10, and sorting those as text puts 10 immediately after 1. Renaming to 01, 02 makes every system agree.

What happens to the image data

Photographs are placed at quality 92, which is visually indistinguishable from the original at normal viewing sizes and keeps the file to a sensible size. Images with transparency go in as PNG so nothing is flattened onto a guessed background.

One consequence worth knowing: a JPEG goes through one more compression cycle rather than being copied in byte for byte. For a photo that is invisible. For a scan of text, where JPEG artefacts show up as fuzz around the letters, it is worth starting from the highest-quality original you have rather than from something already saved twice.

Up to two hundred at a time

Which covers a scanned book chapter or a full set of application documents. If you already have several PDFs to join rather than images, merge PDF is the tool for that, and it copies the pages across without touching them.