Pages follow the order in the list. Move images up or down before you create the PDF, for example receipts by date.
A4 and US Letter centre each image with a margin. Same size as image makes each page the size of its picture, which is best for screenshots.
Photos taken in portrait are often stored sideways with a rotation flag. The tool applies that flag so the page looks like the photo did on your phone.
Large photos make large PDFs. If the result is too big to email, resize the photos first or run the PDF through compress.
The Xargaar PDF Toolkit merges, splits, reorders, rotates and compresses PDFs, turns images into a PDF and adds page numbers. Files stay on your device. The free version produces up to 100 pages per output file.
Open the free PDF ToolkitNo page limit and offline use: the one-time $19 offline pack is here: https://xargaartools.gumroad.com/l/pdf-toolkit-offline-pack