Here is a modification of your script that produces the graphs at two graphs per page. It does this by creating a picture of the 2 graphs, and then adding that to the journal, not the original graphs.
Names Default To Here( 1 );
dt = Open( "$SAMPLE_DATA/Fitness.jmp" );
obj = Logistic( invisible, Y( :Name ), X( :RstPulse ), By( :Age ) );
jour = New Window( "The Journal", <<journal, vlb = V List Box() );
// Loop through the outputs and put them into the journal
// as an Outline Box....to set the title
// and a picture of 2 of the logistic plots
// If the number of plots produced is an odd number, then
// don't allow the script to error out by using Try() on the second
// graphs in each loop
For( i = 1, i <= N Items( obj ), i = i + 2,
ob = Outline Box( "OB", hlb1 = H List Box() );
ob << set title( Report( obj[i] )[Outline Box( 1 )] << get title );
hlb2 = H List Box();
hlb2 << append( Report( obj[i] )[Picture Box( 1 )] );
ob << set title(
Char( Report( obj[i] )[Outline Box( 1 )] << get title ) || " & " || Char( Report( obj[i + 1] )[Outline Box( 1 )] << get title )
);
Try( hlb2 << append( Report( obj[i + 1] )[Picture Box( 1 )] ) );
hlb1 << append( hlb2 << get picture );
vlb << append( ob );
);
obj << delete;
jour << Save Presentation( "fitness_logistic.pptx" );
Jim