You're referring to the CID font system!
Open the file and ignore the warning (or select "Substitute"). Select the text. cidfont f1 f2 f3 f4 f5 f6
When a PDF reader says: "Cannot find or create the font 'F4'" , it means the /Font dictionary resource is missing. The PDF expected a fourth CIDFont but none was embedded or aliased to a system font. You're referring to the CID font system
During this subsetting and embedding process, the PDF engine assigns generic, sequential aliases to the fonts to keep the internal code clean and standardized. represents the first font subset processed. F2 represents the second font subset. When a PDF reader says: "Cannot find or
Beyond aesthetics lies utility. A succinct list like this travels well across systems and scripts, a portable blueprint for documents, PDFs, or embedded resources. It signals modularity: swap f4 for an alternative, add an f7, toggle a bold weight — the structure endures. In that economy of expression there’s beauty: clarity without ornament, a design ethic that trusts function to carry feeling.