These types of dialog messages are generally occurring to indicate that a document is being prepared for reading. But when it takes a long time and comes again and again, it's mean there are a few internal issues. So you don't need to think more how to remove this error because a few simple steps are explained in this article.

How to Disable Please Wait While the Document is Being Prepared for Reading Acrobat

You only need to follow 3 or 4 simple steps which help you to remove the content preparation progress message. I am explaining the method for Adobe Reader 8.

• Just open the following folder- C:\Program Files\Adobe\Reader 8.0\Reader\plug_ins
• Here you will see several folders and files. Delete the file "Accessibility.api" for move it to somewhere else
  
  
  
  
• For next time you will get a one-time message when use Adobe reader. Check the box "Do not show this message again" and click the OK button.
  
  
  
  

Conclusion:

Above suggested steps are enough to the disable content preparation progress dialog in adobe acrobat. Still, if you are getting this message in future, then contact to Adobe tech support or use any other PDF reader program. If the PDF file is very large and takes too much time to open then you can split PDF file online to make them readable. You may also share your feedback through comment.