Image → PDF Converter

Drop in as many images as you like, reorder them, pick a page size — A4, Letter, A3 or A5 — an orientation, a margin in millimetres and a fit, and get a PDF with one image per page. The PDF library is 380 KB, so it is fetched on your first Generate rather than on page load; nothing is uploaded either way.

The three fit modes do genuinely different things, and only one of them is safe by default. Contain scales the image to sit inside the margin box, which means it also enlarges a small image to fill that box: a 200-pixel-wide picture spread across the 190 mm available on A4 is printing at 26.7 dpi, and it will look it. Cover fills the box in the other direction and therefore crops whatever does not fit. Original ignores the page entirely and treats the pixels as 96 dpi, which is fine for a screenshot and a trap for a photograph — a 3000-pixel-wide image comes out 793.75 mm across, so on A4 it is placed starting 827 points off the left edge and only the middle 26.5% of it survives on the page. If the image is bigger than a screen, contain is the mode you want.

PNG files keep their transparency: the page carries a soft mask, so a logo on nothing stays on nothing rather than on black. Every other format is handed to the PDF as JPEG, which has no alpha channel, so a transparent GIF or WebP arrives flattened. Nothing is re-encoded when it does not have to be, so a JPEG photograph is embedded byte-for-byte and the PDF ends up roughly the size of the images that went into it. The exception is a phone photo whose EXIF tag says to rotate it: the PDF would ignore that tag and lay the picture sideways, so it is redrawn upright and re-encoded at JPEG quality 92 instead, as is every format other than JPEG and PNG.

One small imprecision worth knowing if you measure the result: the layout arithmetic uses Letter as 216 × 279 mm while the page itself is written at the exact 215.9 × 279.4, so images on Letter pages sit 0.2 mm above centre. On the A sizes the numbers are exact and the centring is too.