compare two pdf files (approach) using java

compare two pdf files (approach) using java

i need to write a java class that compares two pdf files and points out
the differences(differences in text/position/font) using some sort of
highlighting. my initial approach was use pdfbox to parse the file using
pdfbox and store the extracted text using in some data structure that
would help me with comparing. Is there any java library that can extract
the text,preserve the formatting,help me with indexing and comparing.Can i
use tika/ google's diff-match for this. tika extracts text in the form of
xhtml but how can i compare two xhtml files?