AWS SDK for iOS is depreciated now; so I believe the documentation link also must have been taken out.
Version 1 of the AWS Mobile SDK is deprecated as of September 29, 2014
and will continue to be available until December 31, 2014. If you are
building new apps, we recommend you use Version 2. If you are working
on existing apps that use Version 1 (1.7.x or lower) of the AWS Mobile
SDK, you can download v1 for Android here and iOS here. The API
reference guides are included in the respective downloads. Apps built
using Version 1 will continue to function after December 31, 2014.
However, we highly recommend that you update your apps to the latest
version so you can take advantage of the latest features and bug
fixes.
Source : http://aws.amazon.com/mobile/sdk/
I managed to find a sample code from AWS Mobile Blog [http://mobile.awsblog.com/post/Tx15F6J3B8B4YKK/Creating-Mobile-Apps-with-Dynamic-Content-Stored-in-Amazon-S3] to get the S3 object, you can extrapolate from there.
-(void)getRemoteImage:(AmazonS3Client*)s3
withName:(NSString*)imageName
fromBucket:(NSString*)bucketName
{
S3GetObjectRequest *request =
[[S3GetObjectRequest alloc] initWithKey:imageName withBucket:bucketName];
S3GetObjectResponse *response = [s3 getObject:request];
[self storeImageLocally:response.body withName:imageName];
}
Download Link for v1 iOS SDK : http://sdk-for-ios.amazonwebservices.com/aws-ios-sdk-1.7.1.zip