Sorry for the delay in response.
As per the issue description mentioned above, you are unable to type accented characters in Acrobat XI and Acrobat DC on Mac, is that correct?
Are you trying to type accented characters in for ex. text box, sticky notes under Comment in Acrobat?
Have you tried holding down the character which you want to accent and continue holding the letter until a menu with character accents are displayed? Does that work?
Also, let us know dot version of Acrobat and Mac OS versoin installed on the machine? You may refer to the steps given in this link on how to check the version in Acrobat: Identify the product and its version for Acrobat and Reader DC
You may also visit the following forum threads discussing the issue which seems similar:
I tried typing accented character in a sticky note in Acrobat Pro DC on Mac OS High Sierra. Please find below the screenshot for the same:
Let us know if that is not the case.