When you upload a file it can be assingned the following permissions: READ, WRITE, READ_ACP, WRITE_ACP, FULL_CONTROL (for more information go to: http://docs.amazonwebservices.com/AmazonS3/2006-03-01/S3_ACLs.html#Permissions).
There are three different ways to set the file permissions.
Customer by e-mail. For example:
<fjxau:AccessControl EmailAddress="firstname.lastname@example.org" Permission="FULL_CONTROL" />
Canonical user. For example:
<fjxau:AccessControl ID="qfwejs24a52fe8ca5bef65f89a64e01sdasdasdewf9b1c61be666e9" DisplayName="johnsmith" Permission="FULL_CONTROL" />
Group. For example, to set all the users with READ permission, use:
<fjxau:AccessControl URI="http://acs.amazonaws.com/groups/global/AllUsers" Permission="READ" />