Only a "subset" of the font was included (just the characters used in that file), and your viewer cannot reconstruct the rest.
The font information was lost or corrupted during file extraction or saving. How to Fix "CIDFont+F1" Missing Font Issues cid font f1 f2 f3 f4 f5 f6 f7 fonts better free download
The labels , are internal abbreviations assigned by the PDF exporter to differentiate between various font styles or weights used in that specific document (e.g., F1 might represent Arial Bold, while F2 represents Arial Regular). Why You See the Error The "Missing CIDFont" error typically occurs because: Only a "subset" of the font was included