Retain PDF version and format
Rather than rewriting the PDF to version 1.3 (stand alone), or 1.6 (Acrobat). It would be nice if the same PDF version was retained in the newly imposed PDF file. This would be especially useful when the original PDF contains transparency. Also helpful would be to retain the same PDF object structure. This would benefit those in the variable data printing world who use the PDF/VT format to optimize their rip caching when printing.
Doesn’t it help to choose PDF version while saving imposed documents? Its like you make a new PDF file – you don’t choose it version until you save it.
Sherry Baker commented
YES! The previous versions of Acrobat don't do "live transparencies" so the imposition is useless for press as flattening causes white box issues.