Gmail has added a new feature which let's you insert files from Drive directly into an email without leaving your Gmail. Moreover with Drive you can insert files up to 10GB. And since you send a file stored in the cloud all the recipients will have the same, up-to-date version of it.
Just click the "Insert files using Drive" button in the Compose box and choose the file you want to send.
If you try to send a file which isn't shared with everyone you'll be prompted with the option to change the file's sharing settings.