Greenshot - Greenshot is a free and open source screenshot tool that allows annotation and highlighting using the built-in image editor.
ApowerPDF - ApowerPDF is a versatile PDF editor which also features as PDF converter, viewer, creator and more. It provides a perfect solution for all users.
Capture2text - Capture2Text enables users to quickly OCR a portion of the screen using a keyboard shortcut.
Icecream Apps PDF Editor - Excellent powerful tool to edit PDF, annotate PDF, redact, protect and more.
ksnip - Ksnip is a Qt based cross-platform screenshot tool that provides many annotation features for your screenshots. - DamirPorobic/ksnip
Atril - Atril is a simple multi-page document viewer. Atril is a fork of Evince.