Many pdf readers, editors and tools can split and merge pdf files.
Since 490 MB is a way too big for pdf, I would try to reduce the pdf size by reducing the page size(resolution) also, not just by splitting, because it will be easier that way for e-reader too.
You can use k2pdfopt app (Mac version), both for reducing the page size (e.g. exactly for your reader screen size and resolution) and splitting the pdf into several parts (from page x to y).
k2pdfopt automatically crops the white borders, reduces the page size and cuts the pdf pages to fit e-reader's screen in landscape or portraite perfectly.
http://www.willus.com/k2pdfopt/
https://www.mobileread.com/forums/sho...d.php?t=144711
some other free pdf apps
http://www.willus.com/k2pdfopt/pdf_conversion.shtml