Various links

https://en.wikipedia.org/wiki/Text_shaping

https://github.com/harfbuzz/harfbuzz

https://www.npmjs.com/package/mupdf

https://ehubsoft.herokuapp.com/psviewer/

https://opensource.adobe.com/dc-acrobat-sdk-docs/standards/pdfstandards/pdf/PDF32000_2008.pdf

https://medium.com/@jberkenbilt/the-structure-of-a-pdf-file-6f08114a58f6