If the CMap is missing or corrupted for F2 , the PDF will render question marks or blank spaces, even though the font is technically embedded.
Understanding CID fonts and their F1, F2, F3, F4 resource naming is crucial for anyone working seriously with PDF documents, especially those containing East Asian text. While the naming convention may seem arbitrary or confusing at first glance, it represents a well-thought-out system for managing multiple font resources in a compact, predictable manner.
You'll see F1 , F2 , F3 , F4 when:
When a CID font is embedded, it requires a "ToUnicode" mapping table. This table tells your computer: "When the user copies the visual shape under ID #452, paste it as the letter 'A'." If this table is missing or corrupted during export, the text looks fine on screen but copies and pastes as complete gibberish. 3. Outdated PDF Viewing Software