Cidfont F1 F2 F3 F4 F5 F6 Jun 2026

CID (Character Identification) fonts are a type of font format used in PostScript and PDF documents. The CID font system was developed by Adobe Systems Incorporated to support Asian languages, particularly Chinese, Japanese, and Korean (CJK).

/F1 << /Type /Font /File /path/to/NotoSansCJK-Regular.ttc >> ; /F2 << /Type /Font /File /path/to/NotoSerifCJK-Regular.ttc >> ; /F3 << /Type /Font /File /path/to/SourceHanSans-Normal.otf >> ;

A vulnerability existed in Adobe Acrobat’s CoolType.dll (the font parsing engine). When a malicious PDF defined a CIDFont as /F4 with a corrupted CIDToGIDMap stream, it triggered a heap overflow. The exploit used F4 specifically because few documents have four distinct CIDFonts, and the parser allocated a predictable memory chunk for it.

When a PDF reader says: "Cannot find or create the font 'F4'" , it means the /Font dictionary resource is missing. The PDF expected a fourth CIDFont but none was embedded or aliased to a system font.

This usually means the print job expects multiple CIDFonts, but only the first is available.

In early digital typesetting, fonts could only hold 256 characters (8-bit encoding). This was perfectly fine for the English alphabet, but it completely failed for East Asian languages (Chinese, Japanese, and Korean, collectively known as CJK) which feature tens of thousands of unique characters.

When a PDF creation tool (such as Adobe Acrobat, Microsoft Word's PDF exporter, or a LaTeX compiler) generates a document, it creates an internal font dictionary. /Font << /F1 10 0 R /F2 15 0 R /F3 22 0 R /F4 28 0 R >>

doc = fitz.open("suspicious_document.pdf") page = doc[0]

A standard PDF can have /F1 for a TrueType font. But a will have a /CIDSystemInfo dictionary. Look for:

pdffonts document.pdf

For those who want to go deeper, it's helpful to know the different types of CIDFonts.

Click and print. This sends a flat visual snapshot to the printer, eliminating font decoding errors. Method 2: Re-distill the PDF (Fixing Copy-Paste and Search)

If a PDF uses poorly encoded cidfont+F1 through F6 streams, the document becomes unsearchable. When you press Ctrl+F and type a word, the PDF reader searches for standard Unicode characters. If the internal CID mapping is broken, the reader cannot match your search terms with the generic font subsets embedded in the page. 3. Printing Overload and Delays