Job Description Overview We are seeking an experienced Microsoft Word Add-in Engineer to design and build enterprise-grade Microsoft Word VSTO add-ins using C# and .NET. This role requires deep expertise in Word automation, Open XML, and performance optimization for large, complex documents. You will work on advanced document workflows, secure web integrations, and high-fidelity document transformations. Key Responsibilities • Design, develop, and maintain Microsoft Word VSTO add-ins using C# / .NET • Build custom Word Ribbon UI components, including tabs, groups, and callbacks • Integrate secure web applications inside Word, handling authentication and message passing • Implement section-level editing restrictions and protection policies • Develop reliable routines to extract and replace document sections without breaking formatting, styles, numbering, or tracked changes • Use Open XML SDK for high-performance, bulk document transformations • Optimize add-ins for large documents (50+ pages) by minimizing COM calls and avoiding UI freezes • Implement DOCX ⇄ XML ⇄ PDF conversions with high fidelity and enterprise reliability Key Responsibilities VSTO Add-in Engineering (C# / .NET Core) • Design, develop, and maintain robust Microsoft Word VSTO add-ins. • Implement stable COM interop patterns with defensive error handling and deterministic resource cleanup to ensure reliability in enterprise environments. Custom Ribbon & User Experience • Create custom Word Ribbon tabs, groups, and controls. • Implement Ribbon callbacks and user interactions aligned with business workflows. Web Application Integration within Word • Embed and integrate secure web experiences inside Word using supported hosting mechanisms. • Handle authentication, deep linking, and secure message passing between the add-in and embedded web applications. Section-Level Permissions & Protection • Programmatically define and manage section-level editing restrictions in Word documents. • Enforce read-only regions, user/group-based permissions, and protection policies while preserving document integrity and enterprise security compatibility. Document Section Operations (Extract & Replace) • Implement reliable routines to extract and replace document sections, including headers, footers, fields, content controls, and tracked changes. • Safely handle complex edge cases such as linked headers, multi-column layouts, section breaks, and numbering continuity. Word / Excel Object Model & Open XML Expertise • Leverage the Open XML SDK for high-performance, bulk document transformations. • Ensure round-trip fidelity between Word automation and Open XML-based processing. Performance Optimization at Scale • Optimize add-ins for large documents (50+ pages). • Minimize COM round trips, avoid Selection-based operations, batch updates, and disable UI refreshes where appropriate. • Offload heavy document transformations to Open XML to prevent UI freezes and application instability. Format Conversion (DOCX ⇄ XML / PDF) • Implement high-fidelity document conversions: o XML: Structured reads/writes using Open XML SDK. o PDF: Word SaveAs automation for client-side fidelity; design alternative conversion pipelines where Word is unavailable. We are a company committed to creating diverse and inclusive environments where people can bring their full, authentic selves to work every day. We are an equal opportunity/affirmative action employer that believes everyone matters. Qualified candidates will receive consideration for employment regardless of their race, color, ethnicity, religion, sex (including pregnancy), sexual orientation, gender identity and expression, marital status, national origin, ancestry, genetic factors, age, disability, protected veteran status, military or uniformed service member status, or any other status or characteristic protected by applicable laws, regulations, and ordinances. If you need assistance and/or a reasonable accommodation due to a disability during the application or recruiting process, please send a request to HR@insightglobal.com.To learn more about how we collect, keep, and process your private information, please review Insight Global's Workforce Privacy Policy: https://insightglobal.com/workforce-privacy-policy/. Skills and Requirements Required Qualifications • Strong experience with C# and .NET (Core/Framework) • Hands-on experience building VSTO add-ins for Microsoft Word • Deep understanding of the Word Object Model and COM interop • Proficiency with the Open XML SDK • Experience working with large, complex Word documents in enterprise environments • Strong focus on performance, stability, and resource management Preferred Qualifications • Experience with Office or hybrid web-based Word integrations • Familiarity with enterprise document security and compliance • Experience designing document automation or content management solutions