is a substitute or internal alias for common system fonts like (often the bold variant) or Times New Roman CIDFont+F1 issue - Adobe Community

The error is a handshake problem between a PDF and a printer's memory. It sounds complex, but the fix is usually a simple memory flush or a font outline conversion.

: If the font isn't embedded correctly, characters might be rendered as individual graphical glyphs, significantly increasing the PDF's file size. ✅ Recommended Solutions CID+ Fonts - Adobe Community

Many users on the Adobe Community suggest opening the file in a basic viewer like macOS Preview and then using File > Export as PDF to "re-bake" the document and fix the encoding.

: "F1" is not a specific stylistic font family like "Helvetica." It is a label used by the PDF's internal resource list when the original font information is lost or restricted.