For the Submit button:
It depends a little on what it is you want the Submit button to do on the form.
There are different types of Buttons in the Object Library, that allow you to do different things. Like send a filled in PDF back to an email address, or just the data that's been filled in etc.
In simple workflows, where you want to email the PDF back to an email address you can:
Alternatively you can use the Email Submit Button to do the same.
Let us know what settings you are currently using for Submit button and what it is you are trying to submit (data, PDF etc.), and we'll hopefully be able to help you more.
An additional question. When you save the PDF forms you create in LiveCycle Designer, what application are you testing them in?
Are you testing them in Adobe Acrobat Reader, or Adobe Acrobat for desktop computers? Keep in mind that LiveCycle Designer forms won't work as intended in all PDF viewers, but work best in Adobe PDF viewers.
The Print Form Button should trigger the Print dialog box in Adobe Acrobat Reader or Adobe Acrobat. The person viewing the PDF can then select printer and set appropriate printing options before actually printing the form.
I cannot find any available buttons, nor an Object Library, nor an Insert heading. I am working in Acrobat Pro DC, Creative Cloud 2017. Can you point me in the right direction please?