Because the Internet Browser (Opera Browser) does not support PDF files, when you open a PDF file, a white screen appears.
Please press the BACK button to return to the previous page.
This issue will be fixed with Android OS7(N). Please perform the software update.
For how to update, refer to: How to perform a software update.
You can also view the PDF by opening it on your smartphone and displaying the screen of the smartphone on your TV.
To learn how to display your smartphone screen on the TV, refer to the following Q&A:
How to play back the content stored in a mobile device on the TV screen.