When you add text in a PDF, by default Acrobat picks nearby font attributes for the new text. Similarly, when you edit existing text in a PDF and the font is not available on the system, by default the font fall-backs to a specific font in a particular script; for example, font fall-backs to Minion Pro in roman script fonts. This default behavior can lead to fonts with an inconsistent appearance in a PDF document. To make it consistent throughout all the PDFs, instead of using the default settings, you can choose a specific font for both Add Text and the fallback option in edit text features using the Font Options under the Content Editing preferences.
To restore the default behavior, select Let Acrobat choose in the drop-down list.