Long-press on a document. A menu will appear.
Tap Move or Copy in the menu.
Select the destination where you want to move or copy file.
Tap Move or Copy in the top-right.
To move or copy multiple documents:
Tap on “Select” in the top-right to enter the selection mode.
Tap on the documents you want to move or copy.
Use the buttons at the bottom to move or copy. You may need to tap “More” before finding some options.
Select the destination as above.