A PDF document signer is a tool that allows users to electronically sign PDF documents. Signer. Digital offers a secure and efficient way to sign documents without the need for physical signatures. The process involves applying a digital signature to the PDF document, which can be verified using a public key infrastructure (PKI). This ensures the integrity and authenticity of the document, making it legally binding. In this video, you learn the top 4 benefits of using a PDF Document Signer.