: Open the PDF in Apple Preview (macOS) and then use File > Export as PDF . This often re-flattens the document and restores readability.
Sometimes, browser-based viewers (like Chrome or Firefox) handle CID encoding differently than desktop apps. Try dragging the file into your web browser to see if the text renders correctly. 5. Font Substitution Cid Font F1 Normal Free Download
The person who created the PDF didn't "embed" the fonts, so your computer is trying to find a font it doesn't recognize. : Open the PDF in Apple Preview (macOS)