When your system encounters F1 , it tries to find a matching font. If none exists, you get:
| Standard Name (PDF) | Free Alternative (URW/Ghostscript) | Usage | | :--- | :--- | :--- | | (F1 often) | Nimbus Sans | Sans-serif standard | | Times Roman (F2 often) | Nimbus Roman | Serif standard | | Courier (F3 often) | Nimbus Mono | Monospaced standard | | Symbol / ZapfDingbats | Standard Symbols | Mathematical/Icons |
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 across different PDF generators. One program’s F1 could be another’s F3 . They are simply arbitrary tags. cidfont f1 f2 f3 f4 gratis
Use a free tool like qpdf or mutool (from MuPDF) to decompress the PDF, find the /Font object containing /F1 , and change its /BaseFont or /Subtype to a free CIDFont installed on your system. Recompress.
In PDF syntax, fonts are referenced by internal names. A typical PDF content stream might look like this: When your system encounters F1 , it tries
When processing a PDF that references /F1 without embedding the font data:
Replace the path with your free font’s location. These labels are across different PDF generators
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: . 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.