I’m a software engineer born and raised in Belgium, I love working on hard problems. When I’m not coding, I’m likely riding my motorcycle, climbing or catching some waves!
$DAY_JOB
Currently I’m working as a software engineer for Apryse on the iText SDK and the related product suite. I’m also a member of the PDF Association, working to advance and improve the PDF specification.
Consulting
As one of the core developers on the iText SDK, I’m knowledgeable about PDF’s and document workflows. This includes but is not limited to:
- Document generation, modification
- PDF-UA, PDF-A compliance as required by the eu and US
- Html 2 Pdf Conversion
- Digital signing and signature validation
If you need iText-development hours, tailored training, code reviews, or custom solutions, drop me an email or ping me on WhatsApp!
Technical blog posts
- 2025-08-13 Supporting apache xml in GraalVM
- 2026-04-18 Java syntax highlighting sample
- How I Made PDF Table Rendering 95% Faster in an Afternoon - A blog about optimizing a key bottleneck in the table rendering engine.
- Want to Make Your PDFs 20% Smaller for Free? - A practical article on how we implemented experimental brotli compression in the iText SDK to reduce PDF file sizes without any cost to users.
Talks and Presentations
- GIDS2026 Your Users Are Not Just Human: Designing Systems for People and LLMs - A session about building real-world systems that work well for both human users and AI/LLM-driven workflows.
- Technical Poster at PDF Days Europe 2025 - A showcase of the poster work recognized at PDF Days Europe 2025, focused on practical PDF engineering insights. Download poster here
Projects
- Html 2 well tagged pdf - One of the first implemenations in the world which is able to convert html to fully a fully valid WTPDF build on top off iText
Next step: See engagement options · Invite me to speak
Contact
The fastest way to understand whether I can help is to send a short note about your PDF problem, your stack, and where things are getting painful.
- Email: guust[dot]ysebie[at]gmail[dot]com
- Whatsapp: +32 49 298 34 21
- GitHub: github.com/guustysebie
- LinkedIn: Connect on LinkedIn