The Cid Font family consists of 5 fonts, labeled F1 to F5, each with a distinct character:
You're looking for information on the Cid Font, specifically the F1, F2, F3, F4, and F5 versions, and how to download it for free. Here's what I found: Cid Font F1 F2 F3 F4 F5 Free Download
The phrase typically refers to internal character identifiers used in PDF files, rather than actual downloadable font families. The Cid Font family consists of 5 fonts,
: Use a PDF editor like Smallpdf or Adobe Acrobat Pro to select the broken text blocks and manually change the font to a standard one you already own. labeled F1 to F5