IE rendering engine make use of MSHTML (IE rendering engine) to convert HTML to vector images. From the images, we will render the PDF document. Microsoft has changed its behavior from IE 9 and above, that IE may generates bitmap images instead of vector images. From the bitmap images, we could not extract the text details. So, that the bitmap image may rendered in the PDF document. If bitmap image is rendered in the PDF document, the tags will not be added for the contents.
To overcome this behavior, we have to enable legacy drawing from the registry settings. Please follow the steps in below KB or use advanced legacy drawing tool to avoid bitmap PDF document. Once you enabled legacy drawing, you will get an output document with text selectable. The tags for the content will be added on the PDF document.