DOCUMENT CAM SCANNER - PDF CONVERTER is the best document scanning, editing, and converting app available in the Google Play store. You can use it to scan, edit, and convert all kinds of paper and PDF documents from your smartphone or tablet. You can easily edit scanned documents such as make the font bigger or smaller, change color and background, add text, merge pages, add a border, etc. 

The best thing is that it is free and it is compatible with Android and Windows Mobile. 

This app supports scanned pages of almost all types: business cards, receipts, receipts, receipts, invoices, letters, reports, presentations, etc. In addition to that, you can also use this app to convert PDF files to the respective formats (such as Word, PDF, HTML, etc.). 

For a more advanced experience, you can import scanned pages from a flash drive or SD card. You can also use it to scan or photograph an image.