I believe this what you are looking for, also on that page there are related information links that may assist as well.
How do I save a PDF copy of my tax return in the CD/download edition of TurboTax? - https://turbotax.community.intuit.ca/replies/2985586
How do I get my 2018 tax return copy
If you used our TurboTax online to complete your 2018 return and have not used our Free version you can click here to find your return - https://ww2.2018.turbotaxonline.intuit.ca/?_swlg=en