There is a donation ware service that uses DropBox API that will give you an email address to send files to DropBox. It's got some reviews and appears to be reasonable secure. You can use the email option in Pages to send files this way.
I just tested it and it works for me. I added the new email address to my own entry in the Address Book for easier entry, and one less thing to remember.
Looks better than the SendToDropbox solution. At least for apps that have webDAV capability. I'll have to sign up myself. Having both might be best. Photos doesn't do webDav