STP (Scan To PDF) is a tiny tool which can create PDFs from scanned pages or separate JPEGs.
If you have a scanner, click "Scan New Page", choose your device, and STP will import the scanned page (via the existing driver). You can then deskew, rotate, crop or resize the image as required, before repeating the process to add as many pages as you need.
Once you're ready, clicking "Make PDF" will quickly produce the final document with your preferred JPEG quality setting (high if it must look great, low if you need the smallest possible file size).
As a bonus, STP also includes a "JPEG(s) to PDF" feature, where the program imports your chosen images and saves them all to PDF in a single operation. This works, but it doesn't give you any control over how each image is processed.
STP didn't create documents with one image per page, either, as we were expecting; instead it packed as many JPEGs onto each page as would fit.
STP is basic, and short on configuration options. It has more page tweaking functionality than we'd expect from a portable 282KB tool, though, and if you need to create PDFs from any convenient PC then the program might be useful.