PDF-XChange Editor - The smallest, fastest, most feature-rich PDF editor/viewer available
GImageReader - gImageReader is a simple Gtk/Qt front-end to the Tesseract OCR Engine.
ScanTailor - Scan Tailor is an interactive post-processing tool for scanned pages.
Adobe Scan - Scan anything into a PDF using your mobile device.
Briss - Cross-platform application for cropping PDF files in a simple and fast way via a GUI.
Adobe Acrobat DC - Make your job easier with Adobe Acrobat DC, the trusted PDF creator. Use Acrobat to convert, edit and sign PDF files at your desk or on the go.