[alekswebnet]

Updated the README to clarify features and benefits of the PDF.js viewer.

Summary

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Validation

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Checklist

• The change is focused and includes tests for behavior changes.
• Relevant tests and the build pass locally.
• Public API, behavior, or user-guidance documentation is updated where needed.
• Accessibility impact has been considered, including keyboard navigation and focus visibility.
• This pull request does not disclose a security vulnerability.