F5 F6: Cidfont+f1 F2 F3 F4

You are trying to open a file (like an Illustrator or PDF document) and your computer doesn't have the original fonts installed.

This means: The PDF has at least two CIDFont subsets. +f1 might be a subset of NotoSansCJK-Regular, +f2 a subset of NotoSansCJK-Bold.

In Adobe Acrobat or Illustrator, try manually replacing F1 and F2 with Arial , Tahoma , or Times New Roman . cidfont+f1 f2 f3 f4 f5 f6

If you see these names in the middle of a story you are reading, it usually means the text formatting has "broken," and you are seeing the file's internal metadata instead of the actual characters. How to Fix It

mutool show document.pdf font

Here is a review and technical breakdown of the string "cidfont+f1 f2 f3 f4 f5 f6" .

Output example:

This is an excellent and highly technical topic. The notation cidfont+f1 , cidfont+f2 , etc., is specific to and PDF internals, usually observed in PDF stream dumps , PostScript printer logs , or extracted font debugging output .