# Description of Changes This PR fixes PNG signature application issues in the PDF signing workflow. ## What was changed - Reworked signature application to create locked and printable PDFium stamp annotations with dedicated appearance streams. - Removed the use of `FPDFPage_GenerateContent()` from the signature workflow. - Preserved the signature's original position and dimensions when converting from the viewer's top-left coordinate system to PDF coordinates. - Added CropBox-aware coordinate conversion for PDFs whose visible page origin differs from the MediaBox origin. - Improved signature image extraction to handle internal EmbedPDF asset references and nested image data. - Refactored PDFium bitmap creation so image objects can safely be transferred to annotations. - Corrected PDFium bitmap ownership and cleanup to prevent duplicate destruction. - Added a PDFium WASM integration test covering: - Existing page-content preservation - Stamp appearance generation - Signature coordinates and dimensions - Printable, read-only, and locked annotation flags - Persisted image data taking precedence over internal asset references ## Why the change was made Applying a PNG signature previously regenerated the complete page content through PDFium. This could corrupt existing vector or font-based page elements, including the university logo reported in the linked issue. The previous coordinate conversion also relied only on the page height and did not account for CropBox offsets, allowing the applied signature to move from its preview position. Creating a PDFium stamp annotation with its own appearance stream avoids regenerating existing page content while retaining the selected signature position and size. Closes #7083 --- ## Checklist ### General - [ ] I have read the [Contribution Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md) - [ ] I have read the [Stirling-PDF Developer Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md) (if applicable) - [ ] I have read the [How to add new languages to Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md) (if applicable) - [ ] I have performed a self-review of my own code - [ ] My changes generate no new warnings ### Documentation - [ ] I have updated relevant docs on [Stirling-PDF's doc repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/) (if functionality has heavily changed) - [ ] I have read the section [Add New Translation Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md#add-new-translation-tags) (for new translation tags only) ### Translations (if applicable) - [ ] I ran [`scripts/counter_translation.py`](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/docs/counter_translation.md) ### UI Changes (if applicable) - [ ] Screenshots or videos demonstrating the UI changes are attached (e.g., as comments or direct attachments in the PR) ### Testing (if applicable) - [ ] I have run `task check` to verify linters, typechecks, and tests pass - [ ] I have tested my changes locally. Refer to the [Testing Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md#7-testing) for more details.
Stirling PDF - The Open-Source PDF Platform
Stirling PDF is a powerful, open-source PDF editing platform. Run it as a personal desktop app, in the browser, or deploy it on your own servers with a private API. Edit, sign, redact, convert, and automate PDFs without sending documents to external services.
Key Capabilities
- Everywhere you work - Desktop client, browser UI, and self-hosted server with a private API.
- 50+ PDF tools - Edit, merge, split, sign, redact, convert, OCR, compress, and more.
- Automation & workflows - No-code pipelines direct in UI with APIs to process millions of PDFs.
- Enterprise‑grade - SSO, auditing, and flexible on‑prem deployments.
- Developer platform - REST APIs available for nearly all tools to integrate into your existing systems.
- Global UI - Interface available in 40+ languages.
For a full feature list, see the docs: https://docs.stirlingpdf.com
Quick Start
docker run -p 8080:8080 docker.stirlingpdf.com/stirlingtools/stirling-pdf
Then open: http://localhost:8080
For full installation options (including desktop and Kubernetes), see our Documentation Guide.
Resources
Support
- Community: Discord
- Bug Reports: GitHub Issues
Contributing
We welcome contributions! Please see CONTRIBUTING.md for guidelines.
This project uses Task as a unified command runner for all build, dev, and test commands. Run task dev to get started running the editor, run task to see the most common commands, or see the Developer Guide for full details.
For adding translations, see the Translation Guide.
License
Stirling PDF is open-core. See LICENSE for details.

