PDFTK random order

I'm using the unix pdftk package to merge multiple pdf documents together into a single file with the terminal.

pdftk *.pdf cat output merged.pdf

This merges the pdf files correctly but ordered on name. I'd like to 'shuffle' this and order the different pdf's random. The pdf's pages have to be in order, just the order of the different files has to be random.

How can i achieve this?