Is there a way to print (or export, or save as PDF) all mail messages between specific dates in Gmail?
I realize I could probably do it through an email client, but I would rather be able to through the web interface that I use daily.
James Ferreira wrote a Chrome App for that and used Google Apps Script for it:
Gmail Print All PRO
Gmail Print All Pro is here to help you quickly export messages right to a Google Doc that you can print, save as a pdf, share with others, or store in a way that works for you. Built to be simple to use, all you do is add messages to a Gmail label and run Print All from your Chrome Web Apps screen. This will create a Document in Google Drive containing the content from your messages and you can even choose to have the attachments saved in the same folder.
It used to be free a charge, but nowadays a little fee is required. Program is said to have 22000 weekly users.
Note: I'm not affiliated to Gmail Print All PRO
I'm not sure how you would easily print all of the results, but you could find them by searching for:
after:2012/01/01 and before:2012/12/31
Obviously, you would replace the dates with your own.