Combine photos into one PDF
Receipts for an expense claim, the pages of a form you photographed, a handwritten letter: this is how to put them into one PDF on your own computer, in the order you want.
Adding the photos
Open PDF Assembler and drop the photos onto the window, or click the drop area to choose them. PNG, JPEG, TIFF, GIF, BMP and WebP all work, and HEIC works on a Mac. A TIFF with several pages and an animated GIF become several pages. On a Mac you can also drag photos straight out of the Photos app, and each arrives as the full-size photo. On either system, a screenshot or a picture copied in a browser can be pasted onto the window with ⌘V or Ctrl+V.
You can drop a whole folder too. Its files come in sorted by name, and files in its subfolders are left out. Photos can share the list with PDFs and text files, so a cover letter, two scanned pages and a signed contract can all end up in the same document.
Photos from an iPhone
iPhones save photos as HEIC by default. The Mac version of PDF Assembler adds those directly, but the Windows version can't add them, even on a PC that opens them itself. The simplest fix is on the iPhone: in Settings, Apps, Photos, set Transfer to Mac or PC to Automatic, and it hands your PC JPEGs when you copy the photos over with a cable.
Putting them in order
The file at the top of the list becomes the first page. Sorting by name puts IMG_2 before IMG_10, and since cameras and scanners number their files in order, that's often all it takes. Drag anything else into place.
Switch to Pages to see every page as a thumbnail. A photo that came out sideways can be rotated there, and a blurred one deleted. Ctrl+Z, or ⌘Z on a Mac, undoes either.
What goes into the PDF
Each photo gets a page of its own, portrait or landscape to match, and turned the right way up. The hidden details a phone stores in a photo, such as where and when it was taken, are left out of the PDF.
Keeping the file a sensible size
Phone photos are big. At the Original quality each one goes in at its full size, so a PDF of twenty photos can easily run to tens of megabytes. On the Save step, set Quality to Smaller, which re-encodes the images at a high quality and is usually plenty for reading on screen, or to Smallest for the lightest file. The Saved screen then shows how much smaller the file got. There's more on this in making a PDF smaller.
About PDF Assembler
PDF Assembler is a small app for macOS and Windows that merges, splits, compresses and password-protects PDFs on your own computer. It makes no network requests at all. It's paid once, with no subscription, and the store links are on the product page.
Other guides: Make a PDF smaller without uploading it, Merge PDFs on Windows without Acrobat.