Is there a way to give the user the option to stop the print job before it is actually sent to their printer so they can go back to enter the missing information -- such as an app alert saying something like "Do you want to cancel this print request to fill in missing information? Yes/No"? I'm using Acrobat XI Pro on Windows 7.
No, the information you found is correct: You cannot cancel a print job
once it's started. There is no way around this.
What you can do is change your document while its being printed so that
it's obvious that the form was not filled out completely. What I've done is
the past is to have a watermark in the document that says something like
"Form not filled out completely", or something that would indicate the
state of the document, and then enable that watermark while the document is
being printed, and then disable it again just after the print process
finishes. You can do this using the Document Will Print and Document Did
You can't cancel a print job but if the user tries to print the file from a button that is in your form (that is, not from the built-in command in the application) then you do have full control on whether or not to call the print method. However, once it's called it can't be cancelled using a script.