Which file format is suitable to use when sharing a legal contract that requires a digital signature?

The PDF (Portable Document Format) is the most suitable file format for sharing a legal contract that requires a digital signature. This is primarily because PDFs maintain the formatting of documents across different devices and platforms, ensuring that the contract looks the same for every recipient.

Additionally, PDFs support digital signatures, allowing users to sign documents electronically in a secure manner. The integrity of the document can be verified, which is critical in legal contexts where authenticity is essential. This makes PDFs not only convenient for distribution but also reliable for preserving the legal validity of documents that require signatures.

While other formats like DOCX can be used to create contracts, they may not preserve the formatting as effectively when shared and can be edited easily, which could compromise the legal standing of the document. HTML is primarily designed for web content and would not provide a straightforward way to implement digital signatures. XML, while useful for data representation, does not inherently support functionalities like digital signing in the context of legal documents. Thus, the PDF format stands out as the ideal choice for this scenario.