Hi
You can only edit the PDF if you have the fonts installed on your computer.
To find out what fonts is used and what font you are trying to edit, with the edit document text tool you was using highlight the text and either right click or control click and choose properties, you should now be able to see what font is being used.
If you really want to edit the name, you can chose a new font, one that you have on your computer from the list,and then you will be able to edit the text, in the properties you can also do all other edits such as side and colour etc
Hope this helps