Locked Out Font Adobe Pro

Hello,

I am having an issue with a user in my office. They attempted to edit a PDF recieved from an external graphic design agency and when clicking on a text box and attempting to type it changes the font automatically showing the font used by the agency as greyed out at the bottom. I have added the font into the users device through the windows font options and also through Adobe and still the font is locked.

Is there any kind of lock and external agency can use in order to stop us from editing a document?

Any help would be appriciated if anyone has had something similar.