I frequently see the Content Preparation Progress window pop up (in Acrobat Pro 2017), but then the process freezes right at the beginning, i.e. at Ready. I then have to use Cancel to unfreeze it and then, of course, no Content Preparation takes place.
Does anyone have a fix for this? Perhaps Adobe?
Sorry for being late in answering your query.
As you are getting Content Preparation Progress message in Acrobat, please try the steps given in this link: Hide the message Content Preparation Progress when opening a PDF file
Keep us posted with the results.