In the last days I was working in an app that permits to send the homework made by children by taking the pictures with the Android phone and sharing directly in PDF format.

The App has also the option to reduce the size of the images in order to reduce also the size of the final PDF.

The app is free to use, there is a litle AD on the PDF, you can purchase the PRO version for a little amount directly from the App to remove the AD on the generated PDF.