If you need the text to be processed immediately and as privately as possible - use offline text recognition feature.
Launch an app, create a new document, or open photos from Gallery, tap Recognize and select Plain Text. After a couple of seconds, you will have a saved TXT file (without the source formatting).
The text recognition takes place on your device without any communication with the server and supports 63 languages. You can select up to three different languages for a single document.