Munging PDF files and pages

Having scanned over a dozen handwritten pages from my notebook into a PDF file, I had to invert every other page to make it possible to read the whole thing. It took me a while to find the answer, but YOU can go straight to the solution!

The command line is

pdftk.exe scannedfile.pdf cat 1 2S 3 4S 5 6S 7 8S 9 10S 11 12S output readablefile.pdf