You can upload multiple documents, to the 'Document Center' or in a 'Meeting'.
Click this link to watch a video on how to upload multiple documents in the document center.
See the following steps on how to upload multiple documents in the 'Document Center' :
To 'Drag and drop' you will need to open the folder you are wanting to pull upload documents from. When both windows are open, you can highlight the documents you want, and drag to the square - 'Drag and drop files here'
Once the documents have been uploaded, you will be prompted to 'move' to the desired folder, if finished, then de-select the documents by un-checking each document box.