In my summer, 2014 semester Berklee Online Sibelius course, one of my students asked me to comment on page size specifics for method books and parts for ensembles. Below are my responses.

1. Question:  I am working on an instrumental method book (both self-published and published by a music company). Are there any general guidelines regarding page formatting and printing?
Reply: When I am working on a method book that is going to be published, I check with the publisher and ask for their page requirements. If they don’t have requirements or if I am self-publishing, I go with a standard page size so I can print it on my own printer and get them binded at a local FEDEX or UPS store or print shop.  You can also send the pages in PDF format and get them spiral bound. This is the preferred way to bind music books in small quantities as they stay open easier than traditional binding. There are many services that offer spiral binding, for example:
http://smartpress.com/offering/spiral-bound-booklet-printing

2. Question: Is there a standard format for printing parts for ensemble players?
Reply: I usually go with a standard page size – the default that Sibelius uses. However, if there are a lot of notes on a page, I sometimes print the parts on 9.5 X 12.5 page size. That is the standard music paper size from most publishers. The issue here is unless you own a high-end printed you have to out-source the printing at a FEDEX or a UPS store. Also, it is a good idea to get a slightly heavier weight of paper for parts. See the specifics in the  article mentioned below.

Reference: