Open your PDF in → Go to File > Properties > Fonts tab. Look for entries like CIDFont+F1 , CIDFont+F2 , etc. The "Actual Font" column will show the true name (e.g., "Ryumin-Light").
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: Since these aren't real font files, downloads from unofficial sources may just be bundled unwanted software. How to Fix the Issue CID font F1 F2 F3 F4 F5 F6 F7 Fonts Free Download