Cannot see comments - Error message Cannot extract font

I received a PDF file with comments but cannot access them. When I click on Tools > Comments, I get the message "Cannot extract embedded font PHPBJS+FranklinGothic_DemiCond. Some characters may not appear or print correctly" (the wording may be different as the message was in French). The PDF text appears correctly but there are no comments. Is there anything I can do to see the comments? Thanks for your help.