.... I would like to join them as one pdf file. Is this reasonable to join pdf files or is it better to create one pdf of all the information from the start?
This, I think, depends partly on the total scribus file size.
If the scribus file is unmanageably large, then split it up,
set the page numbers on each part, and export separate pdfs
which can then easily be reassembled.
Scribus chokes on book-length file sizes, in my experience so far.
I routinely export pdfs from many scribus
files which contain my separate chapters and assemble them using PDFtk.
There are lots of pdf managers out there which will assemble many pdfs
into one file, so this is not a problem at all. I do it routinely and often, and
do it again with the revisions just as often.
jack