You do not need to download "F3." You need to download a CJK font family (like Noto Sans or Source Han) and map your missing font to that file.
The document looks correct on screen but prints incorrectly.
If the missing "F3" relates to a Japanese or Chinese PDF, the original font was likely part of the or the Source Han Sans / Noto Sans CJK family.
Be very cautious when clicking "Free Download" links for CID fonts on obscure repository sites. Since CID fonts are complex and rarely used by average consumers, malicious actors often disguise malware or adware as these files. If you download a .exe or .zip file claiming to be a CID font, there is a high probability it is a virus.