How to Reverse the Page Order in a PDF File

If someone scans the pages of a document in the wrong order then the resulting PDF file will have its pages in reverse order. On Linux this is very easy to fix. First install pdftk (if necessary):

  sudo apt-get install pdftk

Then enter:

  pdftk file1.pdf cat end-1 output file2.pdf

where file1.pdf is the name of your input file and file2.pdf the name of the ouput file.

(Thanks to emilien at Stack Overflow)