Order is the part that goes wrong
Merging is easy. Getting the pages in the right order is the actual work, and it is where most online tools quietly fail you, because they take whatever sequence the browser gave them and build the PDF without showing you.
Browsers do not sort files. When you select a folder full of images, the order that arrives is whatever the operating system's file enumeration produced. On Windows it is often close to alphabetical. On macOS it is often creation order. On a phone photo picker it is usually the order you tapped them in, which is at least predictable.
So the list above the export button shows the real page numbers, and the arrows move things. Check it before you export. It takes five seconds and saves reassembling the document afterwards.
Two ways to save yourself the reordering
- Rename first.
01.jpgthrough12.jpg, with the leading zero, because10sorts before2without it. Then select them all and most systems hand them over in that order. - Tap in order. In the iOS and Android photo pickers, the sequence you tap is the sequence you get. Slower, but it is exact.
Page size for a merged document
| Setting | What each page looks like | Best for |
|---|---|---|
| Fit the photo | Exactly the shape of that image. Pages vary in size. | Read on a screen, photo albums, portfolios. |
| A4 | Every page 210 by 297 mm, photo centred and scaled. | Anything going to a printer outside the US. |
| US Letter | Every page 8.5 by 11 in, photo centred and scaled. | Anything going to a printer in the US. |
A mixed batch of portrait and landscape photos is the case where Fit looks strange, since the pages keep changing shape as you scroll. For anything with more than about six mixed pages, A4 or Letter reads better even on a screen. Pages are rotated to landscape automatically when the photo is wider than it is tall.
Receipts, expense claims and forms
The most common reason to merge images is that a form wants one file and you have eleven photos. Two practical notes for that case.
Watch the file size cap. Portals often stop at 5 or 10 MB. Eleven full resolution phone photos will blow through that. Set Quality to Smaller file and check the size shown after export before you go and upload it.
Keep the originals. A PDF made at Smaller file is not a substitute for the photos, and if the claim gets queried six months later you will want the untouched files. This tool never modifies what you dropped in, so as long as you do not delete anything you are fine.