When uploading a file to S3, can you give everyone permission to read/download?

If you are giving read permission to all files in that bucket, we recommend adding a policy to that bucket.

Go to http://awspolicygen.s3.amazonaws.com/policygen.html and select "GetObject" in Actions, type arn:aws:s3:::yourbucketname/* in ARN, and press the Add Statement button.

Next, click the Add bucket policy button in Permissions in Bucket Properties.

If you insert and save the policy you created in the first step, all the files in that bucket will behave as public.