GImageReader - gImageReader is a simple Gtk/Qt front-end to the Tesseract OCR Engine.
ShareX - ShareX is a free and open source program that lets you capture or record any area of your screen...
Adobe Scan - Scan anything into a PDF using your mobile device.
Greenshot - Greenshot is a free and open source screenshot tool that allows annotation and highlighting using the built-in image editor.
Tesseract - Tesseract is an optical character recognition engine for various operating systems
LightShot - The fastest way to take a customizable screenshot.