If you are using the TurboTax online editions have not yet filed the 2018 tax return then you will need to pay the TurboTax account fees before you can print the tax return.

To pay the TurboTax online account fees by credit card, without completing the 2018 return at this time, click on Tax Tools on the left side of the online program screen. Then click on Print Center. Then click on Print, save or preview this year's return. On the next page, to pay by credit card, click Pay Now. On the next screen just click on the Continue button. The next screen will show a review of your Fees, click on Continue. Complete the next screen to pay by credit card and click Continue.

Every year, before mid-October, print a copy of your current year tax return and save it as a tax file and pdf, too.  That way you will have it when you need it for school, a loan, next year’s tax return, etc. without going through a lot of aggravation (and expense)  to get it.

https://ttlc.intuit.com/questions/1899645-how-do-i-save-my-2018-turbotax-online-return-as-a-tax-data...

https://ttlc.intuit.com/questions/1912544-how-do-i-save-my-2018-turbotax-online-return-as-a-pdf

See the following FAQ.

How do I save my 2018 TurboTax Online return as a PDF?

Once you have saved your tax return as a PDF you can view or print it with Acrobat Reader.