TurboTax does NOT currently have the capability to attach a PDF file of a brokerage statement (or any other PDF file) to a return. Only the professional packages can do this (ProSeries, ProConnect, Lacerte).
What you were doing was importing the information from the brokerage statement into the actual return itself to populate Form 8949 and Schedule D. Just the numbers are imported, not the form itself.
If you choose to enter summaries for each category of transaction, you must send the brokerage statement to the IRS, with Form 8453 as a transmittal. TurboTax will give you instructions when you have completed entering the transaction summaries.
It may take the IRS a few years to catch up with you if you don't send in the brokerage statement and Form 8453. They are currently sending out letters for 2018 returns.
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