A company allows customers to upload PDF documents to its public e-commerce website. Which of the following would a security analyst most likely recommend?

Enabling malware detection through a Unified Threat Management (UTM) device is the most direct and effective recommendation for scanning customer-uploaded PDF documents. A UTM integrates multiple security functions, including antivirus and anti-malware, allowing it to inspect files for malicious content before they are stored or processed. This directly addresses the risk of customers uploading infected documents that could compromise the e-commerce site or other users. While other options have security benefits, they are less directly applicable to this specific threat: Utilizing attack signatures in an IDS primarily detects known attack patterns in network traffic, not necessarily malware embedded within files. Limiting affected servers with a load balancer improves availability and can distribute traffic, but it doesn't prevent or detect malware uploads. Blocking command injections via a WAF protects against web application vulnerabilities, but a WAF's primary function isn't deep file content inspection for malware.