The PDF download can be opened by any compatible PDF viewer, such as Adobe Reader.
To access your prior year online tax returns sign onto the TurboTax website with the User ID you used to create the account - https://myturbotax.intuit.com/
Start the 2024 online tax return by entering some personal information then click on Tax Home on the left side of the screen.
On the Tax Home webpage -
Scroll down to the section Your tax returns & documents. Click on the Year and Click on Download/print return (PDF)
if you have only the xxx.tax201X files, those can only be opened by that year's app which is no longer available.
if you need them quickly, there is a service that you can e-mail the files to and you get back PDFs of the returns, this company is not affiliated with Turbotax. Use at your own risk
if you can wait, you can file form 4506 with the iRS to get copies of the return. there is a fee of $30/return
https://www.irs.gov/pub/irs-pdf/f4506.pdf
or you can request a transcript of the return using either
1) form 4506-T by mail
https://www.irs.gov/pub/irs-pdf/f4506.pdf
2) or download a copy by registering or accessing your account if already registered.