A family of Microsoft word processing software products for creating web, email, and print documents.
I don't know if this will help with your specific issue, but thought I would put this here.
I have a large Word document (Word for Mac 2011) with multiple section breaks, however they are all in portrait. I've been working off of this document for years. Over the last month, when I printed to PDF or Preview, the document split into separate files at each section break. Very frustrating having to piece the files back together, when I never had to do this before!
I just found the solution for my problem though!
Go to Print (Command+P), select Page Setup... (under the preview pane), and set Settings to Microsoft Word as the default. Mine was set to Page Attributes, which is what causes it to split at the section breaks.
I don't know how my default got changed to Page Attributes, but changing it to Microsoft Word fixed the issue I was having.
Hope this helps someone else.