The “F” numbers (F1, F2, … F7) appear in or inside PDFs that reference a printer’s internal ROM fonts.
If you open a Korean (KSC) or Chinese (GB1) PDF, your F1-F7 tags will map to totally different fonts (e.g., Batang or SimHei ). Always check your PDF’s font properties first. Executive Summary: Proceed with Caution 1
CID (Character Identification) fonts are a type of font used in PostScript and PDF files. They are also known as CID-keyed fonts. CID fonts are used to represent a large number of characters, often in multiple languages, and are commonly used in Asian languages such as Chinese, Japanese, and Korean. often in multiple languages