By default, Adobe Reader opens a right-hand “Tools Pane”, which is basically a bunch of stuff it wants to sell you. It’s more like a “Tools Pain“, because it hogs a huge amount of screen real estate, especially on laptops.
Here’s how to default Adobe Reader DC to opening with the Tools Pane closed:
1) Open Adobe Reader
2) Open a .pdf document in Adobe Reader DC.
3) Shift+F4 (or click the arrow to the left of the Tools Pane) to close it.
4) In the top menu, click “Edit”, then click “Preferences”.
6) Click “Documents” (under Categories)
7) Checkmark “Remember current state of Tools Pane.”
8) Click the “OK” button.
That does it–until the next Adobe Reader update. It tends to turn the Tools Pane back on, so you might have to repeat this procedure.
(This document is relevant as of Adobe Reader DC version 2018.011.20038)