[scribus] large pdf file

[Ray]

Hi Folks,
As an 82 yr old I have a task from someone to edit a large 500page, 
300+MB PDF file.
I know Scribus opens pdf files but not this one, presumably 'cause of 
its size.
I have tried other programs too but they won't open it either.
I am using Mint 17.1 OS and Scribus 1.4.3.svn.
Is there some way (or pdf program) I can use to open the file and maybe 
break it down into smaller groups of pages, so that Scribus will then 
open it for editing?
Ned