A PDF using Adobe-Japan1 CID font might embed:
If a document requires both Latin characters and Cyrillic characters using a standard F1 font, conflicts arise. The font does not inherently know which code page to reference without complex re-encoding, often resulting in "garbage characters" (mojibake). cid font f1 f2 f3 f4 better
In the context of a PDF’s internal structure (specifically the /Font dictionary), F1 , F2 , F3 , and F4 are or font aliases . They are not specific fonts (like "Noto Sans CJK" or "SimHei"). Rather, they are placeholders that the PDF renderer uses to differentiate between multiple CID font instances within the same document. A PDF using Adobe-Japan1 CID font might embed:
How to Fix PDF Fonts Automatically for Accessibility ... - PDFix cid font f1 f2 f3 f4 better