A free program for Android, by TopTap Studio.

The free Document Scanner app for Android is an all-in-one scanner that allows you to scan, create PDFs, save, organise, and share your scanned documents and photos. You can use it to scan receipts, class notes, bills, book pages, articles, business cards, and many more.

The app has been designed to be extremely simple to use. Simply tap to start scanning and choose a document to scan. After scanning the document, you will be able to save the PDF file and export it to other formats.