As an admin, you can upload documents (.txt, .xls, .doc, .pdf) to your Events, Fundraiser, Groups, etc. These docs will then be displayed as a link when users view the item, so they can download the attachment.
As an admin, go into Edit the group, event, etc. To the right you will see Uploaded Files link. Click on that and upload your document. You can also upload images as well, and those images will displayed to users viewing the item.
Any user who can view the Event, Group, etc. can view/download the attached docs.
Please don't upload any confidential information, as uploaded files are not encrypted.