librepdf/openpdf ? reverse-engineered prompt

Build me a Java library for working with PDF files that can create new PDFs, edit existing ones, render PDF pages to images, and encrypt documents. I also want a way to turn simple HTML and CSS into PDFs for things like invoices, reports, and printable documents.

Please make it feel like a real reusable library, with clear examples I can copy into a project, and include a small Kotlin friendly option too. It should support text, fonts, tables, images, page size and orientation settings, and basic PDF reading and writing. If it makes sense, add a simple demo or toolbox app so I can try the features quickly.

Keep it open source friendly and well organized, and if you need to check current docs or best practices online, go ahead. I mostly want something that works cleanly, is easy to use from Maven, and covers the common PDF tasks without being overly complicated.