You’ll find shady sites offering “CID font F1.otf” or “F2.ttf”. because:
https://support.adobe.com/en/faq/faq.html?id=kb:en_US:fa368e3b-f6f4-4b84-b3f2-44a5a8d39fb1:fa368e3b-f6f4-4b84-b3f2-44a5a8d39fb1 cid font f1 f2 f3 f4 f5 f6 f7 fonts free download link
Google Noto Sans CJK and Noto Serif CJK are open-source, support CID mapping, and cover F1–F7 styles. You’ll find shady sites offering “CID font F1
When you see names like F1 , F2 , F3 , F4 , F5 , F6 , or F7 listed under the fonts section of a PDF's properties, you are looking at [1]. Here is how they work: support CID mapping