Hi Keryn, I see what you mean. There isn't a bulk option for items within the main site structure as it's not common to want to delete things en-masse there.
I thought I'd quickly suggest another option for those PDF's though. You could add a File Set to the site and add the PDF's to the file set. You could have a File Set per term, then delete an old terms' File Set once it's not useful anymore. If you'd rather link through to the google view of the page each day you could use a Link Set instead.
I hope that helps :D Let me know if you need any more info.