When you’re scheduling calendar events it can be useful to associate documents or other files with the event; the agenda for a meeting, say, or the menu for that important dinner.
Google Calendar can’t currently do this out of the box, but you can achieve it by enabling the Event Attachments feature in Labs. To get that done, Go to your Google Calendar and click on the gear icon in the top-right corner of the interface. Select Labs, scroll down and enable the Event Attachments Lab, then save your changes.
You’ll now see a link in the event editor from which you can attach files:
The feature lets you add documents straight from Google Drive or from your own computer. Just remember that guests don’t automatically have permission to view Google Docs attachments, so you should first attend to the sharing of each document you attach.
UPDATE: This feature has now graduated from Labs to be a full calendar feature.