can anyone know with what software we could split a DJVU file into smaller parts?

You may use djvused from the DjVuLibre package for this purpose.
e.g. to select page 6 from a document: <code> djvused infile.djvu -e "select 6 ; save-page-with outfile.djvu" </code>



djvm can be used to concatenate the files, e.g. <code> djvm -c outfile.djvu page???.djvu </code>

thanks Karsten, I will follow your recipe

Does anyone know how to split a landscape 2-up file (two pages per sheet) into a series of 1-up sheets.