Documentation for the PDF viewer: https://www.pdftron.com/webviewer/
pdf.html - is the webviewer with the text document test.html - is the embeded one
To change the path of the pdf go to the script tag in the pdf.html and change the initialdoc: path to change the pdf.
webviewer folder is the full custom webviewer, To import the webviewer use this
<script src="WebViewer/lib/webviewer.min.js"> to make the webviewer run use liveserver to run the html. https://marketplace.visualstudio.com/items?itemName=ritwickdey.LiveServer