Try Documentalist, my app that offers fast, offline access to 190+ programmer API docs.
Long term, I want to write a web-based version of SumatraPDF, SumatraPDF Online.
Replicate the UI and functionality as a web app.
One option for implementing PDF viewer on the web is pdf.js library.
I don't know it very well so today I've spent some time reading the code.
As part of learning process, I've implemented extracting PDF annotation info in JSON and plain text format.
For SumatraPDF I've added advanced setting annotations.defaultAuthor because it was very easy