if the object is simply to create a PDF file, then PDFCreator is a simple open-source program
PDFCreator | Free Business & Enterprise software downloads at SourceForge.net
However all that will do iwith the jpg files is convert the image format from jpg to pdf. Nothing will directly convert the jpg file to an editable / searchable text-based pdf. To do that you will have to OCR it and then convert
PDFCreator will create a searchable PDF once the OCR has been done
if you want to use Amazon's Kindle, then start here at Amazons online publishing site
https://kdp.amazon.com/self-publishing/signin or find their downloadable program at
If you want another format then look at Calibre
calibre - E-book management
But your first problem is extracting the text from those image files
If they are only small it could be easier to retype them