Hello Gary,
You are not obliged to open each drawing one by one (if you open the drawings one by one, you are correct that it is currently closing the Document Manager).
You can use the "Preview" tab from the Document manager to view the drawings one by one (just pick one drawing on the left and you will see its content on the right) without having to open them; in the Preview, you have all the possibilities to pan, zoom in, zoom out, etc. ; you can also stretch the "Document Manager" dialog box to make it bigger and to better see the content of the drawing.
Best regards
Philippe