You can, if your 2020 PDF is a 1040 return generated through TurboTax, H&R Block, or TaxACT software (Form 1040-SR is not supported for PDF transfer).
Be aware that in some cases TurboTax won't be able to read the PDF, for example if it's password-protected or is a scanned copy of a PDF instead of an actual PDF file.
- Sign into your TurboTax account to access returns for 2021
- Choose New Tax Return from the File menu
- Select Start a New Return
- When you get to the transfer screen, select Browse
- Navigate to your PDF file, select Open, and follow any onscreen instructions