> 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/xamarin/low-level-pdf-api.md). # Low-level PDF API - [Low-Level document editing (COS/SDF API) in Xamarin](https://docs.apryse.com/xamarin/low-level-pdf-api/low-level.md): Unlock the power of low-level PDF APIs with Apryse SDK. Gain full access to COS/SDF object model, seamless integration, and unique functionalities for customizing PDF documents. Get started today! The - [Information dictionary: adding custom data to a PDF in Xamarin](https://docs.apryse.com/xamarin/low-level-pdf-api/add-custom.md): Learn how to add custom data to a PDF document using the Cos/SDF low-level API. Get a full code sample demonstrating how to edit existing PDF files effectively. The Apryse Xamarin SDK streamlines secu - [Introduction to PDF file format](https://docs.apryse.com/xamarin/low-level-pdf-api/pdf.md): Learn about the basic structure of a PDF document and its components, including header, body, cross-reference table, and trailer. Dive into the details in this informative guide. The Apryse Xamarin SD - [SDF / COS object model](https://docs.apryse.com/xamarin/low-level-pdf-api/sdf.md): Discover how to navigate and edit complex PDF documents effortlessly with Apryse CosEdit. Explore the SDF/COS object model for precise control over PDF content. Simplify PDF editing with Apryse SDK's - [Filters and streams in Xamarin](https://docs.apryse.com/xamarin/low-level-pdf-api/filters.md): Learn about SDF stream objects and filter pipelines in PDF documents with Apryse SDK. Explore efficient processing methods for compressed and encrypted content. The Apryse Xamarin SDK streamlines secu - [Sample for editing PDFs using basic Cos/SDF API in Xamarin](https://docs.apryse.com/xamarin/low-level-pdf-api/samples.md): Learn how to edit PDF files using the Cos/SDF low-level API with this informative sample. Enhance your document editing skills now! The Apryse Xamarin SDK streamlines secure, serverless document proce - [APIs for low-level PDF document editing in Xamarin](https://docs.apryse.com/xamarin/low-level-pdf-api/apis.md): Discover utility classes for PDF documents in Xamarin.Android and Xamarin.iOS using C# with pdftron.SDF.Obj and pdftron.SDF.SDFDoc. Enhance your PDF handling capabilities now! The Apryse Xamarin SDK s --- # 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/xamarin/low-level-pdf-api.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.