title_body: I am looking for a software or a way to list, extract, count, in short, analyze a book which is in epub or pdf format As someone who is interested in learning languages, I want to find a way to know the each word and their repetitions inside a book that I am going to read.
upvoted_answer: Here is one way to find the number of words in an epub file sorted by their frequency, with the words used the most at the top of the list.  
  
  This is done on a Mac laptop and will also work on Unix hosts. 
  
  The overview of the process:
  
  
  Install Calibre
  Use the ./ebook-convert command in Calibre to convert the epub file to text 
  Transform the entire text file to lowercase (so "Word" and "word" match) 
  Convert punctuation to whitespace (so "period." and "period " match) 
  Convert all whitespace to a new line.  This puts each word on its own line. 
  Exclude any blank lines from the list
  Sort the list of words alphabetically
  Pipe (send) that list of words through uniq -c You now have a count of how often each word appears.
  Sort the result in numerical order.  If you use the sort command with the -r argument, the most frequent words are at the top.
  
  
  Here's an example of steps (2) through (9).  The head command lists the top ten words in the final output.  
  
  $ ./ebook-convert ./book.epub ./book.txt
  $ cat   ./book.txt | tr '[:upper:]' '[:lower:]' | tr "“" " " | tr "”" " " | tr "," " " | tr "." " " | tr " " "\n" | grep -v ^$ |  sort | uniq -c | sort -gr  | head
   5303 the
   1960 and
   1934 of
   1910 to
   1874 a
   1168 i
   1067 you
    844 in
    812 that
    703 it
   $
  
  
  The result is pretty boring.  The word 'the" appears 5303 times, while the word 'it' appears 703 times. 
  
  I suspect in most books the most common words are the tiny conjunctions, articles, prepositions and pronouns.  Perhaps on something that is not a novel this might be more interesting.
  
  Good luck!