Before diving into the "F" designations, it helps to understand what a is. In the digital typography world, CID stands for Character Identifier .
If you are looking to fix display issues or extract these fonts, here is everything you need to know about why they appear and how to handle them. What Are CID Fonts (F1-F5)? Cid Font F1 F2 F3 F4 F5 Free Download
Open Adobe Acrobat and go to > Preferences (or Ctrl + K ). Click on the Page Display category. Before diving into the "F" designations, it helps