PDF Upload/Download via SMS Auth

I need a secure system on my website that allows clients to upload and download PDFs using SMS verification.

Requirements include:
- User Authentication: Clients authenticate via SMS verification.
- PDF Handling: Clients can upload and download one PDF at a time.
- User Interface: Simple and intuitive interface for mobile use.

Ideal Skills:
- Experience with SMS verification integration.
- Familiarity with secure file upload/download systems.
- Web development skills, especially for mobile-responsive designs.

Please provide a portfolio showcasing similar work.