Instead of opening the PDF directly, create a new blank document in your design software and use the or "Import" command to bring the PDF in. This sometimes allows the software to substitute a working system font automatically. Flatten Transparency

In Adobe Illustrator, import the file and use the to convert the problematic text into outlines. This makes the text uneditable but ensures it displays correctly for printing or viewing. Best Sites for High-Quality Alternatives

Because "F1" is just a label (often representing the first missing font found in the document), it could be mapping to anything from to Times New Roman depending on the specific file. How to Fix the CIDFont+F1 Error