Files can be moved between folders in a number of ways:
Drag and drop. This is quickest and easiest. Select the documents that you want to move. Then, while holding the mouse button down, drag them over to the desired folder and release. If you dragged documents from one local folder to another, this action will move the documents – so that a copy of the document is not left in the original location. In external databases such as NCBI the documents will be copied, leaving one in its original location.
Drag and copy. While dragging a document over to your folder, hold the Ctrl key (Alt/Option key on Mac OS X) down. This places a copy of the document in the target folder while leaving a copy in the original location. This is useful if you want copies in different folders. Folders themselves can also be dragged and dropped to move them or instead copied by holding down Ctrl (Alt/Option on Mac OS X).
The Edit menu. Select the document and then open the Edit menu on the menu bar. Click on Cut (Ctrl+X/command+X), or Copy (Ctrl+C/command+C). Select the destination folder and Paste (Ctrl+V/command+V) the document into it.