I'm facing this problem in majority cases while I was sharing the PDF files through Adobe Acrobat, it shows that "loading the documents is error" I don't know why it's coming like that.
I hope someone will say the reason.
As explained above, does it happen with all the files that you load in Acrobat? Check with the different one as it could be a file specific issue.
Where and how you have been sharing the document? Were you emailing it to someone?