Some PDF toolkits may fail to render text if a corresponding CID is missing from the font stream.

To save space, PDF creators often "subset" CID fonts, including only the characters used in that specific document. This can sometimes cause issues when trying to edit the PDF later. Academic and Professional Requirements What are CID or composite fonts?

To develop a feature related to CID (Character ID) fonts, I'll provide an overview of what CID fonts are and potential features that can be built around them.