change a file in a pdf created from multiple files

Is there a way to update one file in a pdf created from multiple files? i.e I have combined 34 files into one pdf (rather time consuming) then tweaked and cleaned up the pdf, but a couple of the files need changing - one has new numbers in it and another has a new print area. Can I just swop in these files or is the only way to re-combine again or remove/add pages?

Appreciate any assistance!