While adding accessibility tag to the pdf file some extra text content (@) added to the pdf file, the sample pdf file's are in following link please find the problem.
Before Add Tags to Document:
http://uploadingit.com/file/avecc8bshs4s792h/Test2_Before_Add%20Tags%20to%20Document%20in%20Acrobat%...
After Add Tag to Document:
http://uploadingit.com/file/5w09yp78zyc39g7e/Test2_After_Add%20Tags%20to%20Document%20in%20Acrobat%2...