diff --git a/README.md b/README.md
index ee49926..a7e0a50 100644
--- a/README.md
+++ b/README.md
@@ -31,6 +31,7 @@ Some options need to be set in `config.sh` file.
 ## pdf2book.py
 This script takes a pdf and reorders pages for printing signatures.
 The number of pages per signature can be varied 
+Dependency: `pypdf`
 ```
 s=1: 1,2,3,4 -> 04,01.02,03  i=0 
                 08,05.06,07  i=1
diff --git a/pdf2book.py b/pdf2book.py
index b265d8c..cc37394 100755
--- a/pdf2book.py
+++ b/pdf2book.py
@@ -1,35 +1,43 @@
 #!/usr/bin/env python3 
 
+from pypdf import PdfReader
+from pypdf import PdfWriter
 import argparse 
 parser = argparse.ArgumentParser(
     prog='pdf2book',
     description='pdf2book rearranges pages for signature printing ',
     epilog='AQOABA')
 
-#parser.add_argument('pdf-file')           # positional argument
-parser.add_argument('pages', type=int)           # positional argument
+parser.add_argument('pdf_file')           # positional argument
+#parser.add_argument('pages', type=int)           # positional argument
 #parser.add_argument('-s', '--signature')      # option that takes a value
 parser.add_argument('-v', '--verbose', action='store_true')  # on/off flag
 parser.add_argument('-s', '--signature', 
     dest='signature', 
     type=int,
     action='store',
-    default=1,
+    default=0,
     help='')
 args = parser.parse_args()
 
-s=args.signature
-if s < 0 : 
+signature_size=args.signature
+if signature_size < 0 : 
 #    print("signature size must be greater than 0!")
     print("signature size must be positive integer!")
     exit(1)
-pages=args.pages
+
+reader = PdfReader(args.pdf_file)
+number_of_pages = len(reader.pages)
+#page = reader.pages[0]
+#text = page.extract_text()
+
+pages=number_of_pages
 #print(pages)
 
 lst=[]
 
-def get_reorder(page_number: int, signature_size: int):
-    panu=page_number
+def get_reorder(number_of_pages: int, signature_size: int):
+    panu=number_of_pages
     sisi=signature_size
 
     #  s|  1 |  2 |  3 |  4 | 
@@ -49,23 +57,23 @@ def get_reorder(page_number: int, signature_size: int):
     #12 | 12 | 16 | 12 | 16 |
     #13 | 16 | 16 | 24 | 16 |
           
-    p=page_number
+    p=number_of_pages
     s=signature_size
-    if s == 0:
-        s=1
-        pages_filled= ( int((p-1)/(4*s)) +1 )*4*s
-        s=int(pages_filled/4)
-    pages_filled= ( int((p-1)/(4*s)) +1 )*4*s
+    if signature_size == 0:
+        signature_size=1
+        pages_filled= ( int((number_of_pages-1)/(4*signature_size)) +1 )*4*signature_size
+        signature_size=int(pages_filled/4)
+    pages_filled= ( int((number_of_pages-1)/(4*signature_size)) +1 )*4*signature_size
           
-    signature_count=int( pages_filled/s/4 )
+    signature_count=int( pages_filled/signature_size/4 )
     #print(signature_count)
     for i in range(signature_count):
     #    print("i=",i)
-        down=(i+1)*4*s
+        down=(i+1)*4*signature_size
     #    print("down=",down)
-        up=  (i*4*s)+1
+        up=  (i*4*signature_size)+1
     #    print("up",up)
-        for count in range(s):
+        for count in range(signature_size):
     #        print("count=",count)
             lst.append(down); down -= 1
             lst.append(up);   up   += 1 
@@ -75,14 +83,34 @@ def get_reorder(page_number: int, signature_size: int):
     #print(lst)
     #print(len(lst))
     return lst
-def print_signatures(lst: list,s: int):
-    if s==0: s=1
+def print_signatures(lst: list,signature_size: int):
+    if signature_size==0: signature_size=1
     for i in range( len( lst ) ):
-        if ( (i+1) % (4*s) == 0 ):
+        if ( (i+1) % (4*signature_size) == 0 ):
             print(lst[i])
         elif ( (i+1) % (4) == 0 ):
             print(lst[i], end=' ')
         else:
             print(lst[i],end='.')
-lst=get_reorder(args.pages, args.signature)
-print_signatures(lst,s)
+lst=get_reorder(number_of_pages, signature_size)
+print_signatures(lst,signature_size)
+
+# REARRANGING OF PAGES
+
+def rearrange_pages(reader, lst):
+
+    writer = PdfWriter()
+    for page in lst:
+#        print(page)
+        if page > len(reader.pages):
+            writer.add_blank_page(width=reader.pages[0].mediabox.width,height=reader.pages[0].mediabox.height)
+        else:
+            writer.add_page(reader.pages[page-1])
+
+    return writer
+
+# SAVE FILE TO DISK
+writer=rearrange_pages(reader,lst)
+outfile=args.pdf_file.split(".pdf")[0]+"_book_s"+str(signature_size)+".pdf"
+with open(outfile, "wb") as fp:
+        writer.write(fp)