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)?
What are you using when you see these font names? (e.g., AutoCAD, a PDF reader, a printer driver?) Are you trying to view a file or create one? Cid Font F1 F2 F3 F4 F5 Free Download
This often "flattens" the font data or re-embeds it, making it readable in other software. Manual Substitution: If you are looking to fix display issues
when saving your PDF to prevent these generic names from appearing for others. Impossible fonts to be found / Fontes impossíveis de achar a PDF reader