How images become PDF pages
For every image you add, in list order, the tool creates one page and draws the picture on it with pdf-lib. It identifies each file by its first bytes (the PNG or JPEG signature) rather than by its extension or reported type, so a mislabelled or extension-less file still works, and anything that is neither is rejected with its file name. Embedding does not re-encode a JPG; the original compressed data goes into the PDF, so a photo keeps its exact quality and the file grows by about the size of the image. PNGs are stored with their alpha channel, so transparent areas stay transparent on the page.
Only JPG and PNG are accepted. A WebP, HEIC or GIF is rejected with a message naming the file. Convert it first with a tool such as PNG to JPG.
The two page-size options
PDF measures pages in points, where 72 points make an inch. This tool maps one image pixel to one point.
- Fit page to each image: the page takes the image's pixel dimensions as points, and the image fills it edge to edge with no margin. A 3000 x 4000 pixel phone photo becomes a 3000 x 4000 pt page, which is about 41.7 x 55.6 inches. It looks fine on screen but prints at a huge scale, and pages may vary in size across the document.
- A4 pages (centered): every page is 595.28 x 841.89 pt (210 x 297 mm).
- US Letter pages (centered): every page is 612 x 792 pt (8.5 x 11 inches).
In both paper-size modes, a landscape image (wider than tall) gets a landscape page and a portrait or square image gets a portrait page. The image is scaled by the smaller of the width and height ratios, times 0.95, then centered, leaving a margin of about 2.5 percent per side. Small images are enlarged too, not just large ones.
Worked example
The same 3000 x 4000 photo on A4 gets scale min(595.28/3000, 841.89/4000) x 0.95, about 0.1885. It is drawn at 565.5 x 754.0 pt with margins of about 14.9 pt at the sides and 43.9 pt at top and bottom. A 4000 x 3000 landscape photo instead gets an 841.89 x 595.28 pt landscape page and is drawn at 754.0 x 565.5 pt, so it uses the page properly instead of floating in a portrait page.
Common mistakes
- Wrong page order. Pages follow the order of the list, which starts as the order you added the images. Drag a row by its ⠿ handle to drop it into a new slot, or tap the ↑ and ↓ arrows if you are on a phone or tablet where dragging rows does not work. The ✕ removes an image.
- Huge output. Since images are not downscaled, a dozen 12-megapixel photos yields a PDF of tens of megabytes. Shrink them first with the image compressor.
To combine the result with other documents, continue to Merge PDF.