How do I print a copy of my 2018 1040 after it has been e-filed and accepted? Or how do I download a .pdf? It is only showing a one page message as the pdf download.

If the PDF download from the Tax Home web page is incomplete then use Print Center.

When you sign onto your online account and land on the Tax Home web page, scroll down and click on Add a state.  See screenshot

 This will take you back to the 2018 online tax return.

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.  Choose the option Include government and TurboTax worksheets

And this year the 1040 is 2 half pages but now print on 1 sheet with the Signature line in the Middle.