Which AWS feature should the company use to share and access the files securely?

Explanations:

Amazon Cognito user pools are used for user authentication, allowing users to sign up and log in, but they do not directly facilitate secure file sharing or access to S3 buckets.

S3 presigned URLs allow temporary, time-limited access to specific S3 objects, enabling secure file sharing with other users without requiring them to have AWS credentials. This is ideal for the requirement of securely sharing files.

An S3 bucket policy controls access to the entire bucket and its contents but does not provide a mechanism for secure file sharing on an individual basis, especially if users need different access levels.

Amazon Cognito identity pools provide temporary AWS credentials for users, but they do not handle the direct sharing of files. They enable access to AWS services but would require additional configurations to share files securely.