Canon i550 User Manual page 46

... Click to pause printing of the specified document.
... Click to resume printing.
... Click to cancel printing of the specified document.
The BJ Print Monitor allows you to change the print order of documents queued for printing.
To change the print order, place the mouse pointer over the name of the document, hold the mouse button down while dragging the
document name to the new position, then release.
When the print order change includes the current job, it stops and the new job immediately starts instead.