Currently, when the PDFViewer is used with the latest pdf.js version 4.0.379 an error is thrown in the browser console. (Uncaught (in promise) Error: No "textContentSource" parameter specified.)

You can test the behavior in the Dojo linked here - https://dojo.telerik.com/@NeliKondova/eBUYEDAb. Run the example and wait for the pdf file to be loaded, then check the browser console. 

The latest Kendo version is compatible with pdf.js version 3.11.174. However, I would like the Kendo UI for jQuery to be compatible with pdf.js 4.x to avoid such misbehaviors.