If you’ve ever extracted text from a PDF or tried to edit a file generated by old or unknown software, you may have stumbled upon a mysterious CIDFont reference: F1, F2, F3, or F4 . These aren’t actual font names like Arial or Times New Roman. Instead, they are placeholders — internal tags used by the PDF’s font dictionary when the original font embedding is missing, corrupted, or deliberately stripped. What Are F1, F2, F3, F4? In PDF internals, a CIDFont (Character Identifier Font) is used for fonts with a large glyph set, often Asian scripts like Chinese, Japanese, or Korean (CJK). When a PDF creator cannot embed the original font, it may substitute a generic CID-keyed font and label it F1 , F2 , etc. These labels are not standardized across different PDF generators. One program’s F1 could be another’s F3 . They are simply arbitrary tags.
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