In your dojo examples of your pdfViewer control you are loading pdf.js version 2.2.2 and with this setting you can select text inside the pdfViewer when the button "enable selection" is klicked.
however, when i try to use the latest version of pdf.js (3.4.120) then the selection of text is not possible
The last Version where it seems to work is pdf.js (3.1.81)
Is this a known Issue? i don't like the idea of having to use such an old version of a js-library. Is this Problem related to kendo or to pdf.js?