https://ttlc.intuit.com/questions/1914214-can-i-print-a-copy-of-my-turbotax-online-return-before-i-file-it
When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s. Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS received the return.