How to convert JPG to PDF without a huge file size?

Download one of the PDF printer drivers, such as Nitro or PrimoPDF, and just open your image in Photoshop and print it with the PDF driver. We use these a lot to make excellent quality, small PDFs to email to customers.

You can try JPEGtoPDF, a very light (236 kB) portable program which converts images to pdf.

According to its web page,

This is a program for converting image files into PDF files. The program supports converting multiple image files to single or multiple PDFs files. The program also supports image scaling and positioning.

This program is now written in VB.Net, and supports additional image formats: BMP, GIF, PNG, TIF, WMF, EMF, in addition to JPG, JP2, J2K. Also, This program now supports commandline execution, where the syntax is: JPEGtoPDF.exe "pdfFileName" "imgFileName1" "imgFileName2"

(Note that every parameter should be a full path+filename, and be enclosed in quotes)

This program now supports unicode filenames.

Latest addition: The program now supports multi-page images.