Is there a way to run the tablet in Ultra Power Saving Mode and still open a PDF file?

[AC Question]

is there a way to run the tablet in "Ultra Power Saving Mode" and still open a PDF file?

I am planning a rock climbing trip, and I downloaded a guidebook to my Galaxy Tab S. I want to use the guidebook on the tablet while we are out there, but the battery probably won't last long enough in the normal power saving mode. Is there a way to run it in "Ultra Power Saving Mode" and still be able to open the guidebook?

Thanks!

Matt