Right because you transferred a pdf. You need the tax data file ending in .tax2018. The tax files (and PDF files) should be in your Documents then in a Turbo Tax subfolder. If you can't find them do a search for all files ending in .tax or .tax2018, etc. And check the Recycle Bin. For Windows 10 check the One Drive. Did you make any backups? Like DropBox.
If you don't have the main .tax file you might have one that starts with a Tilde sign ~ like "~your name.tax2018." That file is if your computer crashes or your real file gets lost or deleted or corrupt so you can restore it.
Find your Tax file in Windows
https://ttlc.intuit.com/community/tax-data-file/help/find-your-tax-data-file-tax-file-in-windows/00/...
Did you use the 2018 Desktop program? Try this.... start the 2018 program and try to open your return. Go up to File-Open. Then save your return and watch where it saves it. Go to File-Save or Save As.
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