Acrobat cannot display ligatures when Illustrator saved as PDF

[lb1996]

I have been working with typeface Acumin Pro and everytime I save my file as a PDF, I notice the "ff" ligature doesn't work and there's a little box instead () when opening from Acrobat. Any idea if this issue is with Illustrator or Acrobat? I shouldn't have to turn off ligatures (although the option doesn't appear, at least for this font) 

[Ton Frederiks]

Do you save your Illustrator file as pdf with Illustrator editing capabilities checked?

[Kurt Gold]

Which version of Illustrator are you using?

Which version of Acrobat are you using?