> For the complete documentation index, see [llms.txt](https://docs.apryse.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.apryse.com/ios/digital-signature.md). # Digital signature - [Digital Signature Validation on iOS](https://docs.apryse.com/ios/digital-signature/digital-signature-validation.md): Validate signatures in signed documents by verifying signers using PTDigitalSignaturesViewController. Learn how to add a trusted certificate and validate digital signatures effectively. The Apryse iOS - [Sign a PDF document on iOS](https://docs.apryse.com/ios/digital-signature/sign-pdf.md): Learn how to digitally sign PDF files with the Apryse SDK, ensuring authenticity and security. Get a full code sample for adding approval signatures to PDF documents using a Digital Certificate. The A - [Adding a certified signature field to a PDF on iOS](https://docs.apryse.com/ios/digital-signature/certify-pdf.md): Learn how to add a certification signature field to a PDF document and digitally sign it with a full code sample. Understand the process of certifying a PDF/A document for compliance. The Apryse iOS S - [Verify a signature on iOS](https://docs.apryse.com/ios/digital-signature/verify-pdf.md): We offer a higher-level document-based API for verifying signatures, as well as a lower-level per-signature API. Page includes code samples. - [Code samples for adding digital signatures to PDFs on iOS](https://docs.apryse.com/ios/digital-signature/samples.md): Digitally sign PDF files with ease using this high-level API. Learn how to sign and certify documents efficiently. Perfect for secure document management. The Apryse iOS SDK streamlines secure documen - [API for digital signatures on iOS](https://docs.apryse.com/ios/digital-signature/apis.md): Learn how to work with digital signatures in PDFs using iOS (Objective-C/Swift) with PTSignatureHandler and PTWidget classes. Enhance your document security now! The Apryse iOS SDK streamlines secure --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation by asking a question. Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters: ``` GET https://docs.apryse.com/ios/digital-signature.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.