Updated (14/09/2018): It's now possible to duplicate multiple pages at once, instead of just one at a time.

Using this script you can duplicate a page in a PDF file one, or more, times, while preserving the form fields on it in tact. There's even an option to automatically rename the form fields so that they could have unique values.
This is a fast and easy way of creating multiple copies of a one-page form, or to set up a file for n-Up printing.

When you run the script you're presented with this dialog window, where you can select which page(s) to duplicate, how many copies to create and whether the fields on those pages should be renamed (so each copy is unique) or not:

When you press OK the tool will immediately duplicate the selected pages and place the copies at the end of the current file.