There is no way to upload documents that will transmit along with your return. Tax forms like your W-2s, 1099s, 1098s, and other needed tax documents, the program will ask you to enter. But outside of those, there is no way to upload personal documents to transmit with the e-file. If there are other documents that the program doesn't ask for, that you need to send with your return, you will need to mail those in. So you would need to print and mail the return with the documents. 

This link will give you the instructions on how to print and mail if you are using the TurboTax Online version of the software, TurboTax for Windows CD /Download software or TurboTax Mac CD/Download software:

https://ttlc.intuit.com/replies/3401713

https://ttlc.intuit.com/replies/3401365

https://ttlc.intuit.com/replies/3401483