Worked on the mozilla/gecko-dev repository to deliver a comprehensive PDF.js library upgrade, focusing on reliability and maintainability within document annotation workflows. Utilized JavaScript to update PDF.js to version 250cc7d299e889aa1c01236cbcebd92571550049, integrating fixes for Bug 1971992 and related improvements. Enhanced the annotation editor by refining edit mode handling and selection logic, which reduced user friction and improved usability. Conducted internal component refactors and systematically updated build and version metadata across multiple files, strengthening release traceability. Collaborated through code review processes to align with cross-team standards, emphasizing clean library updates and maintainable JavaScript code throughout the project.