Specifically, if I take a book from 1880 (obviously in the public domain), scan it, convert it to PDF, and sell it on Ebay as a PDF, do I have any rights under copyright law that could deter someone from buying that pdf from me and turning right around and selling it themselves? Put more abstractly, if a text is in the public domain and my only contribution to it is to digitize it from an old book into a pdf or other format, can the result be copyrighted?

All Answers To Questions

You cannot do this without authorization. If you obtain the PDF for personal use related to normal academic or research activities, that would be entirely different, but commercializing this would be criminal.

you might want to check out the Electronic Frontier Foundation at http://www.eff.org/ I've listed some other links as well that might provide more information.

it being that old it pretty unlikely you will get sued. even though it is possible. however almost all ebooks just up on torrent sites anyway. your trying to sell something that should be free.

You cannot create nor maintain any copyright or proprietary interest in a work which is in the public domain. That is the entire definition of "public domain." You are certainly free to scan the book into PDF files and sell these files for a fee, but you cannot pretend or represent to hold a copyright interest in these works, since the material is in the public domain. You can hold an ownership interest in the computer files themselves, but once you sell the files, any buyer of the file can do as they please with it, including posting their own copy on the internet for further sale at a profit, and you would have no claim to their earnings.

The result cannot be copyrighted. You need to make some contribution to the work itself in order to get copyright. Just the effort of scanning it doesn't count.