One way to work with Journals is to create the empty journal and then add content, which may include reports as well as container objects for layout:
Open( "$SAMPLE_DATA/Big Class.jmp" );
biv = Bivariate( Y( :weight ), X( :height ), Fit Line( {Line Color( {213, 72, 87} )} ) );
dist = Distribution( Continuous Distribution( Column( :weight ) ), Nominal Distribution( Column( :age ) ) );
jrn = New Window( "Reports", <<Journal );
jrn << Append( H List Box( (biv << Report) << Clone Box, (dist << Report) << Clone Box ) );
jrn << Save PDF("c:\test.pdf");