Thanks for posting.
It appears that this question was already answered in the French language forum, here: http://forums.filemaker.com/posts/c4a85fe28d
For other people viewing this thread, this script is using the Append to PDF option which is currently not a function supported by FileMaker Go.
It is a bit dangerous to reply with so little info but you might be able to adapt by using two form layouts, one designed for just one model and then one designed for two models. Think of copying the layout and pasting it on the second page of the layout, below the page break indicator. That raises issues with filling the fields....
Second, if the form is set two show in list view and you have the two records selected they should print as a report rather than as two pages as form view. You would drag the body to the proper position for the page break.