Comment 57 for bug 382379

The problem is in Poppler. The fix I have done in Poppler to allow documents with pages of different sizes sets the page size in each page header. Setting the page size resets the duplex to print on the front side and so it gets never printed on back sides. I have fixed this by checking whether the current page size is different to the size of the previous page and only add a page size request to pages with a new size now.