I am guessing that you are talking about PDF forms and not web forms.
You can manually edit the PDF add copy and paste the submit button as many times as you want. You will need Acrobat to do so.
Instruction for Acrobat XI (probably very similar to Acrobat X):
Open the PDF in Acrobat
Click on File > Save a Copy...
Open the copy you just saved
Click on Tools > Forms > Edit (in the Right Pane)
Find the "Submit Button" and Copy and paste it to other places in your PDF. Make sure you don't change anything else about the button.
File > Save as Other... > Reader Extended PDF > Enabled More Tools (includes form fill-in & save)...
Try the forms and the different buttons on your form.
Hope this helps