Images to PDF

Why bundle images into a PDF at all?

Because almost every institutional process expects one. Visa applications, insurance claims, expense reports, university submissions and rental applications all ask for a single PDF, and none of them will accept a folder of photos. Turning a stack of phone photographs of receipts into one document is probably the single most common reason anyone opens a tool like this.

PDF also fixes the page geometry in a way an image cannot. A photograph has pixel dimensions but no physical size, so it prints at whatever scale the software guesses. A PDF page is defined in points, so an A4 page prints as A4 on any printer in any country.

And a PDF holds order. A folder of images sorts by filename, which is why photos taken in sequence end up as IMG_0012 before IMG_0002 in some listings. Once they are pages, the order is part of the document.

Choosing a page size and fit

"Fit to each image" makes every page exactly the size of its image plus the margin. Nothing is scaled and nothing is cropped, so this is the right choice when the images are the content — a photo album, a portfolio, a set of screenshots. The trade-off is that pages will vary in size, which some printers dislike.

A4 and US Letter give you consistent, printable pages. Each image is scaled to fit inside the margin box while keeping its proportions, and centred, so nothing is ever stretched or cropped. A portrait photo on a portrait page fills most of it; a landscape photo on a portrait page sits in the middle with space above and below. Switching to landscape orientation fixes that.

Margins are in points, where 72 points is one inch. Zero produces a full-bleed page with the image running to the edge, which looks good on screen but will usually be clipped by a printer's unprintable border. Around 24 to 36 points is a safe default for anything that might be printed.

What happens to your images

At original quality nothing is re-compressed: a JPEG is placed in the PDF exactly as it is, byte for byte, and a PNG is stored losslessly. WebP, AVIF, GIF and BMP, which PDF cannot hold, are converted to lossless PNG, so they all work identically and lose nothing.

Choose the smaller-file setting and every image is re-encoded as JPEG instead, at the quality you set. At 85 the difference from the original is invisible for photographs. For screenshots and documents with fine text, push it to 92 or higher — sharp edges are what JPEG handles worst, and text is nothing but edges.

Transparent areas show the white page behind them, because PDF pages have a colour. A PNG logo with a transparent background will appear on a white page rather than on the colour it was designed for.

One consequence worth knowing: the text in a photographed document is a picture of text, not text. The resulting PDF is not searchable and cannot be copied from. Making it searchable requires optical character recognition, which is a different kind of tool.

Keeping the file small enough to send

Modern phone cameras produce 12 megapixel images at 3 to 6 MB each. Twenty of them is well over 60 MB before any page overhead, and most email systems reject attachments over 20 to 25 MB.

The lever that brings that down is the smaller-file setting: a JPEG quality of around 70 typically halves the size with little visible loss on a document photograph, and it shrinks PNG screenshots far more.

If you need a specific target size, compress the images first with the image compressor and then build the PDF from the compressed versions — that gives you far more control than the single quality setting here.