F3 and F4 are the wildcards. They are frequently assigned to:
Why they matter: If F3 or F4 are not embedded, users opening your PDF on a mobile device or non-CJK system will see tofu (empty boxes) instead of text. Making your PDF better means verifying that F3 and F4 are fully embedded if they contain critical data. cid font f1 f2 f3 f4 better
CID (Character Identifier) fonts are used for large character sets (e.g., Chinese, Japanese, Korean – CJK). F3 and F4 are the wildcards
When you export a PDF, the writer sometimes strips the original font name to save space or due to subsetting. If you open the PDF in a text editor or check the Fonts tab in Acrobat Pro, you might see: Why they matter: If F3 or F4 are
CID Font F1 (Embedded Subset)
Type: CID Type 0
Encoding: Identity-H
This tells you that the original font (say, "Adobe Ming Std") has been embedded as a subset and is internally labeled F1.