Here is what you can do in order to edit the text of a scanned document:

1. Download the LetsScan app on your iPhone.
2. Open LetsScan
3. Import the scanned document into LetsScan
4. Open the document in LetsScan
5. Click the “Scan” icon at the tap-bar 
6. The text of your scanned document will be shown as plain text 
7. Edit your text using the editor bar
8. Send your text as PDF, PNG, RTF, and TXT format.

If using LetsScan to scan a document, you will be able to edit your scanned document in LetsScan by following the above procedure, except that you don’t import the file, but you scan it instead.