Alt+5 (Numpad) centers the contents of the document window. Note that the Num Lock key must be toggled off.
The "Open Document" dialog offers previews of the documents that you highlight on the left:
When the preview is long (as in the above screen capture), you might need to scroll it up or down. You can use the scrollbar located to the right of the preview. But you can also use the cursor keys. Clicking the preview, then pressing the cursor keys (Left, Right, Up, Down, Home, End, PgUp, and PgDn) will scroll the preview in the corresponding direction.
See also...
