What does pdf file mean

PDF (Portable Document Format) is a file format that has captured all the elements of a printed document as an electronic image that you can view, navigate, print, or forward to someone else. Essentially, it is a photocopy of a document.

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It is an image of your return.  A PDF file can be opened and viewed on most computers and mobile devices.  You don't need the Turbo Tax program installed to open it.

Why are you asking?  You can (and should) always save your return as both the PDF file and as the tax data file ending in .tax2016