It's not easy moving around to shops where you can scan documents and convert to PDF. People want to do this at their convenience. You can create an app or website that offers this service. You can include premium packages and free packages. You will generate traffic on your website which will earn you some money. That's if you make use of Google AdSense or its equivalent, you can sell merchandise too. Make sure it's something people are interested in. Making money through this process might take some time but you will surely make some money.