GImageReader - gImageReader is a simple Gtk/Qt front-end to the Tesseract OCR Engine.
PDF-XChange Editor - The smallest, fastest, most feature-rich PDF editor/viewer available
Adobe Scan - Scan anything into a PDF using your mobile device.
ScanTailor - Scan Tailor is an interactive post-processing tool for scanned pages.
Microsoft Lens - Microsoft Lens (formerly known as Office Lens) is an all-in-one application designed for Windows, Android, and Apple devices, allowing you to capture important information from signs, PDFs, whiteboards, and more to add.
Briss - Cross-platform application for cropping PDF files in a simple and fast way via a GUI.