It acts as a substitute for fonts that were not fully embedded in a PDF document. The "F1" suffix is just a sequential label (F1, F2, etc.) used by the software to keep track of multiple missing fonts.
: In Illustrator, instead of opening the file directly, create a new document and the PDF. Use the Transparency Flattener cid font f1 ttf free download link
Opening the problematic PDF in a viewer like macOS Preview and then re-exporting it as a new PDF often "flattens" the fonts, making them readable. It acts as a substitute for fonts that
Formula 1 licenses its fonts exclusively through Monotype for commercial use. A single license can cost over $500. instead of opening the file directly
is a technical label for a Character ID (CID) keyed font used in PDF encoding IDRsolutions