Open-source licences
Last updated: October 2026
PaperPDF stands on the work of open-source projects. Thank you to everyone who builds and shares them.
| Software | What we use it for | Licence |
|---|---|---|
| pdf-lib | Building, merging, splitting and stamping PDF files | MIT |
| PDF.js (pdfjs-dist) | Drawing PDF pages for previews, PDF to JPG and compression | Apache-2.0 |
| libheif (via libheif-js) | Opening HEIC / HEIF photos in browsers that cannot do it themselves (loaded only on HEIC pages) | LGPL-3.0 |
| Astro | Building this website | MIT |
| Tailwind CSS | Styling | MIT |
Fonts
Typed signatures use these handwriting fonts. They load only when you open the Type tab of the Sign PDF tool.
| Font | Licence | Licence text |
|---|---|---|
| Dancing Script | SIL Open Font License 1.1 | Read |
| Great Vibes | SIL Open Font License 1.1 | Read |
| Caveat | SIL Open Font License 1.1 | Read |
| Homemade Apple | Apache License 2.0 | Read |
Watermark and page-number text in Hindi, Malayalam or Arabic is drawn with the Noto Sans fonts below. Each file loads only when you type that alphabet. All are under the SIL Open Font License 1.1.
| Font | Licence | Licence text |
|---|---|---|
| Noto Sans | SIL Open Font License 1.1 | Read |
| Noto Sans Devanagari | SIL Open Font License 1.1 | Read |
| Noto Sans Malayalam | SIL Open Font License 1.1 | Read |
| Noto Sans Arabic | SIL Open Font License 1.1 | Read |
About the HEIC converter (LGPL)
The HEIC converter is the unmodified libheif library compiled to WebAssembly. It is a separate file that your browser downloads only when you open a HEIC photo: libheif.wasm and libheif.mjs. The second file is the original library code wrapped so that it can be imported as a module. The licence text is in LICENSE.txt, and the source code is available from the project links above. Because the library is kept as separate files and is not changed, you or anyone else can replace it with another build of the same library.