Do not open the PDF directly. Instead, create a new Illustrator document and the PDF into it.
: If you see an error for "Cidfont-f6," it means the original font (which could be anything from Arial to a custom CAD font) was only partially embedded, and your current software cannot find the original source to display the text. How to Fix the "Missing Cidfont-f6" Error Cidfont-f6 Font Free Download
Click the tab. Look for "Cidfont-f6" in the list; it will often show the name of the "Actual Font" or "Original Font" next to it. You can then search for that specific font (e.g., Arial or Myriad Pro) to download. 2. Use Font Substitution Do not open the PDF directly