When a PDF is created, the software may use to handle large character sets (like Chinese, Japanese, or Korean) or to subset a font to reduce file size. If the receiving software cannot find the original font—such as Arial or Helvetica—it assigns a generic name like CIDFont+F1 or F2 .

Because Noto fonts are CID-keyed and support Adobe’s character ordering (Adobe-Japan1-6), which is exactly what /F1 and /F2 expect. They act as drop-in replacements.