How to display bookmarks in the initial view when opening a PDF file?

I'm looking for a way to modify an existing pdf file so that the bookmarks panel opens automatically (on the right hand side) when I open the pdf file in acrobat reader or another reader. In https://stackoverflow.com/questions/17333412/set-pdf-document-properties-initial-view you can see how this would be done in Acrobat. However, I do not have, or really want Acrobat, and would like a way to do this from the unix command line. I've looked at pdftk and qpdf but can't see how these tools can help me for the moment. Any ideas ? Best regards /Colm