If you have ever dug into the inner workings of a PDF file—especially one containing complex scripts like Chinese, Japanese, or Korean (CJK)—you have likely stumbled upon cryptic labels: CID Font F1, F2, F3, and F4 . These identifiers are not random. They are placeholders for a sophisticated font mapping system. But the critical question every developer, publisher, and archivist asks is: What makes a CID font F1, F2, F3, F4 better than the default?
Use Adobe-Japan1 , Adobe-GB1 (Chinese), or Adobe-Korea1 CMAPs explicitly. Avoid generic Identity unless you control the mapping end-to-end. 5. Repair Broken F1/F2/F3/F4 with Ghostscript or qpdf When you encounter a PDF that shows garbled text due to bad CID labels, use Ghostscript to rewrite the font structure: cid font f1 f2 f3 f4 better
From here, you can extract the raw CIDs and remap them using a known Unicode table, producing a better output than relying on the broken original. Scenario: A government agency had 10,000 PDFs created in 2005. Each file used F1 (Korean), F2 (Chinese), F3 (Japanese) interchangeably. Text extraction was impossible. If you have ever dug into the inner
pdffonts yourfile.pdf Look for the "Type" column: CIDFontType0 or CIDFontType2 . Then inspect the "CMAP" column. If you see Identity-H but the language is Japanese, no direct conversion is possible without a custom CMAP. But the critical question every developer, publisher, and