Embedding fonts allows anyone who opens your file to see the document as you intended it to be seen.For a PDF file with fonts already embedded, you may still need to further edit it. To keep font embedded for both of its original texts and newly added/edited texts after editing,please do the following steps:
1:Please first turn on the embed fonts after document editing option in preferences dialog box by going to "File"tab in Foxit PDF Editor>"Preferences”>"Documents",check option "Automatically embed fonts whever text is updated or saved" ,click on "OK" to save the setting.
2:With this option selected, then proceed to use the "Edit>Add Text" or "Edit>Edit Object>Text" or "Edit>Edit Text" tool to edit texts , or "Organzie> Header&Footers" tool to add/modify headers/footers in PDF file,you will find that the characters (a subset of a font) that are used when you edit text objects or headers/footers in the document will be embedded into the document automatically.
Note:The option "Automatically embed fonts whever text is updated or saved" for embedding fonts after document editing is available in Foxit PDF Editor version 12.0 and greater.