About KitePDF¶
A pure-Kotlin document engine for every platform. KitePDF is a standalone multiplatform library. It reads, views, edits and builds PDFs, and it reads reflowable EPUB 2/3 books. One Kotlin codebase covers Android, iOS, JVM, web and Kotlin/Native. There are no platform wrappers and no native binaries.
Design¶
Most Kotlin PDF libraries are thin wrappers around a platform engine: PdfRenderer on Android, PDFKit on iOS, PDF.js in the browser. Each platform then behaves differently, and a bug can sit in any layer.
KitePDF uses a single engine instead. The parser, renderer, editor, writer, crypto and fonts are written in Kotlin, and almost all of that code is common. kitepdf-core carries three expect declarations: a mutex, a thread id, and the deflate/inflate hook. Nothing else in the engine branches per platform. There is no JNI, no platform PDF engine underneath and no embedded web view.
The Compose binding draws into a DrawScope. Pages therefore scroll, zoom and animate like any other composable, not like an embedded platform view.
Current status¶
KitePDF is pre-1.0. These features work today:
| Area | What works |
|---|---|
| Viewing | Compose viewer with continuous and paged layouts, two-page spreads, RTL progression, pinch-zoom, pan, double-tap, text selection, search highlights, outline panels, link taps |
| Text | Extraction, structured text with geometry, and engine-level search for both formats |
| EPUB | Reflowable EPUB 2/3 on the same core: CSS cascade, embedded fonts (TTF, OTF, WOFF, WOFF2), hyphenation in seven languages, CJK justification, ruby, vertical writing, floats, tables, reader settings |
| Forms | Read and fill text, checkbox, radio and choice fields |
| Annotations | View and interact with highlights, links and comments |
| Encryption | Open, authenticate, edit and create password-protected PDFs (AES-256/R6 on write) |
| Editing and saving | Fill forms, stamp watermarks, redact (the content is removed, not covered), incremental save or full rebuild |
| Building | Text with standard or custom embedded fonts, including subsetting, plus shapes, images and colors |
| Image codecs | Supplied by KiteImage, the shared pure-Kotlin codec engine: PNG, JPEG (baseline and progressive), GIF, BMP, JPEG 2000, JBIG2 and CCITT |
| Signing scaffold | /ByteRange preparation and CMS embedding. The cryptography stays in your application. |
Planned:
- Signature validation
- Advanced color management (ICC application, rendering intents)
- Less common form widgets (media players, rich text)
- More handlers on the shared core (XPS, CBZ, SVG)
Known limits are listed in the README.
Reporting a bad rendering¶
If a PDF renders incorrectly in KitePDF, file an issue with the file attached. The project includes a pixel-diff harness for the JVM/AWT backend, and every rendering fix lands with a regression test.
Contributing¶
Contributions are welcome. Check the GitHub repository for open issues and the developer guide. Code changes, test additions and rendering fixes are especially valuable.
License¶
KitePDF is licensed under the Apache License 2.0. You can use, modify and distribute it in commercial and open-source projects.
A small number of source files contain encoding tables derived from MuPDF by Artifex Software, and those files keep their original AGPL-3.0 headers in comments. They do not restrict the rest of the project. See the source comments for the exact locations.
Standard-14 font width metrics come from URW++ AFM files.