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====== Double-sided printing ======

It is still necessary to print documents. Many printers are able to print one side of the sheets, here I describe the procedure to print both side correctly. The procedure depends on the kind of printer.

===== How-to =====

Make an empty .pdf page:

  $ echo '' | ps2pdf -sPAPERSIZE=a4 - white.pdf

Add an empty page at the end of a document:

  $ pdftk  W=white.pdf D=input.pdf  cat D W  output output_file.pdf

Extract //even//-numered pages from a document (replace the word //even// with //odd// for odd-numered pages):

  $ pdftk  input.pdf  cat 1-endeven  output_even.pdf

Reverse the order of pages:

  $ pdftk  input.pdf  cat end-1  output output_reversed.pdf

===== Case 1 =====

Being ''PPPP'' the printed face, and ''WWWW'' the blank face it is the //case 1// if printing a three pages document the sheets end up like this:

    PPPP
  3 WWWW
  
    PPPP
  2 WWWW
  
    PPPP
  1 WWWW

In other words, the printed pages end up with the face up and the order of the sheets is reversed.


==== Procedure ====

  - Ensure the input file has a even number of pages adding a blank page at the end if needed.
  - Split the file in even and odd pages.
  - Reverse the order of the even and odd pages file.
  - Print the reversed even file.
  - Put the printed sheets back in the printer being careful to align the printing side and top side.
  - Print the reversed odd file.