Image to PDF

How to use it

1. Drop your images onto the box above, or click Choose files.
2. Check the order in the list. Drag rows, or use ↑ and ↓. Remove anything with ✕.
3. Under Page setup, choose whether pages should match each image or use A4 or Letter, and set a margin if you picked a standard size.
4. Click Create PDF, then download it.

How it works

A PDF page is a canvas of instructions, and one of those instructions can be “draw this image here, at this size”. So building a PDF from images does not mean converting anything in the usual sense — it means creating pages and placing an image on each.

PDF is picky about which images it will carry: the format supports JPEG and PNG data directly, and little else that browsers produce. When you add a JPG or PNG, its bytes are copied into the PDF untouched, which is why there is no quality loss and why the resulting file is roughly the sum of your inputs. When you add a WebP, AVIF or GIF, the browser decodes it to pixels and re-encodes it as JPEG or PNG first — one extra step, done once, with the format under your control.

Page sizing is where the two modes diverge. In fit mode each page box is set to the image’s own dimensions, treating one pixel as one point, which is a 72 DPI page. In A4 or Letter mode the page box is fixed and the image is scaled to the largest size that fits inside your margins, then centred. The scale never exceeds 1, so a small image is not blown up and blurred to fill the page.

Very large images are handled rather than left to fail. PDF caps a page at 200 inches on a side, so fit mode scales down anything that would exceed it, and images too big for the browser’s canvas limits are reduced before conversion. A JPEG that pdf-lib refuses — usually a progressive or CMYK variant — is quietly routed through the canvas path instead of erroring out.

Tips

• Name files so they sort in the right order before you add them. The list preserves the order they arrive in.
• For scanned documents, fit mode usually looks better than A4: a scan already has the page proportions, so forcing it onto a fresh A4 page just adds a second set of margins.
• If the finished PDF is too big to email, compress it afterwards rather than shrinking the images first — you get better control and can see the result.
• Photographing a document instead of scanning it? Crop it before adding it here. There is no cropping step in this tool.