doc-view-conversion-refresh-interval

doc-view-conversion-refresh-interval is a variable defined in `doc-view.el'.
Its value is

1

Documentation:
Interval in seconds between refreshes of the DocView buffer while converting.
After such a refresh newly converted pages will be available for
viewing. If set to nil there won't be any refreshes and the
pages won't be displayed before conversion of the whole document
has finished.

You can customize this variable.