Free High Quality PDF Tools includes pdf-lib 1.17.1, licensed under the MIT License.

Project: https://github.com/Hopding/pdf-lib
Pinned source: https://github.com/Hopding/pdf-lib/tree/v1.17.1
Bundled distribution: https://cdn.jsdelivr.net/npm/pdf-lib@1.17.1/dist/pdf-lib.min.js
License source: https://raw.githubusercontent.com/Hopding/pdf-lib/v1.17.1/LICENSE.md
The full license is included in pdf-lib-LICENSE.txt.

The bundle includes these upstream dependencies, with their licenses included:

@pdf-lib/standard-fonts 1.0.0 (MIT) - standard-fonts-LICENSE.txt
https://github.com/Hopding/standard-fonts

@pdf-lib/upng 1.0.1 (MIT) - upng-LICENSE.txt
https://github.com/Hopding/upng

pako 1.0.11 (MIT and Zlib) - pako-LICENSE.txt
https://github.com/nodeca/pako

tslib 1.11.1 (Apache-2.0) - tslib-LICENSE.txt
https://github.com/Microsoft/tslib

pdf-lib is bundled inside the extension. These URLs are documentation only;
the extension does not fetch executable code or other resources from them.