[plug] Converting PDF file from 2-pages in one.

[Mike Holland]

A well-know publisher has been selling documents in PDF format,
with two facing book pages to each (landscape) PDF page.
I emailed them that this was inconvenient, especially on portable 
devices, and got a reply:

   We're currently going through all our content and amending to one page
   pdfs thanks to feedback such as this.
    We're almost through our reformatting our top 100 titles, but as I'm
   sure you can imagine, it's a significant task.

It sounds like they are manually loading each doc into the processor and
"save as PDF" from the menus.
  There must be an easier way! The Unix way - a small script and a filter?
Assuming their publishing software is totally broken, are there any 
(Linux) tools that would convert such a PDF, breaking each landscape
page into two portrait pages?
   Would converting PDF to postscript and back be a bad idea?

Mike