The optimal solution is to use Amazon S3 to store the static digital handbooks and Amazon CloudFront as a Content Delivery Network (CDN). S3 provides durable, scalable, and cost-effective object storage for the files. CloudFront caches copies of these files at edge locations around the world, physically closer to the users. When a user requests a handbook, it is served from the nearest edge location, significantly reducing latency and improving download speeds. This architecture also enhances security by allowing traffic to be served over HTTPS and enabling the restriction of direct access to the S3 bucket, ensuring users can only access content through the secure CloudFront distribution.

A. Amazon Kinesis Data Streams is a service for capturing, processing, and storing real-time data streams, not for hosting and delivering static files to end-users.
C. Using EC2 instances with an Application Load Balancer is a pattern for dynamic applications, not the most efficient or cost-effective solution for delivering static content globally.
D. Amazon EFS is a regional, shared file system for EC2 instances and is not designed for direct, low-latency content delivery to a global user base.

1. Amazon CloudFront Developer Guide: In the "What Is Amazon CloudFront?" section, it states, "Amazon CloudFront is a content delivery network (CDN) service... When a user requests content that you're serving with CloudFront, the user is routed to the edge location that provides the lowest latency (time delay), so that content is delivered with the best possible performance." It also explicitly lists "static asset caching" as a primary use case.

2. AWS Documentation - Getting started with a secure static website: This guide details the reference architecture for this exact use case. It states, "This solution uses Amazon S3 to host the website content and Amazon CloudFront for secure and low-latency content delivery... CloudFront provides a fast and secure experience for the website users." (See: "Solution overview" section).

3. AWS Well-Architected Framework - Performance Efficiency Pillar: Under the best practice "PER 5: How do you select the best performing architecture?", the framework advises: "Use a content delivery network (CDN) to reduce latency by serving requests from a location closer to your customers. A CDN is well-suited for content that is cacheable, such as static web pages, images, videos, and other static assets."