software recommendation - How can I remove the gray-scale page background of a PDF document scan while preserving the text? (Binarization) - Ask Ubuntu
Increase the Contrast of a PDF to Sharpen & Darken Text | OSXDaily
These Are the 10 Best PDF Scanner Apps to Download
scan/fax with text & numbers in black & white - how to improve/cleanup/enhance using Photoshop/GIMP? - Graphic Design Stack Exchange
PCLinuxOS Magazine - Page 12
Scan documents to PDF, Adobe Acrobat
3 Methods | How to Sharpen PDF on Windows/Mac/Online - EaseUS
Scanning Images/Text and Simple Image Editing | YSU
Adobe Acrobat Pro DC Tutorial 8 - Enhance Scans - YouTube