PDF correction?

I've received a pdf from a colleague which has some typographical oddities
w.r.t. IPA characters. Is there any way for me to make corrections or to
determine what was meant? I don't know what font was used originally-- I've
asked him, but it's an old paper so he may not remember.....

Among them are: ® (r in a circle) for (perhaps) glottal stop (though ? shows
up correctly elsewhere) and ¡ (inverted !) for (I think) the velar nasal
(which also shows up correctly elsewhere). These don't seem to be usual
substitutes for Unicode chars., in my experience. (Plus one or two others--
nothing crucial, but it's annoying......)  I think these oddities appear
mainly in the footnotes, not in the text. Any idea why that would be?

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