I have a couple of PDFs and DJVU documents that I want to read on an ereader (namely, Kobo Touch). However, the size of the pages differ, between cover and actual content, and even between two different content pages, and what my ereader does is use the size of the first page as the "template" for the viewport size for all my documents. It means that if the first page is smaller, it will display only a small part of the next (bigger) pages, corresponding to the size of the first page. If the first pages is larger, then the other smaller pages will be tiny on a corner of the screen.
In other words, how can I scale all pages in a PDF/DJVU document to the same size (preferably the largest size among the pages in the document)?
PS: The files are mainly scanned scientific papers, in DJVU format, though I have to convert them to PDF in order to read them in my ereader.