Some more filters:
If you want to trim borders conservatively:
It will only trim pages that actually have borders - use Image -> Trim
Best to do this first (before any other actions such as resize)
If you want to take up the full frame to remove page turning artifacts from the viewer to add borders, for your last step, go to Image -> Canvas Size, enter your screen resolution, and chose a background color (probably white will be good) Make sure for input you are using pixels, and use the center anchor.