As a self-publishing service, Blurb doesn't review, edit or monitor the content of books published using our services. This means we can't tell you if a specific book is in the public domain or otherwise legal for you to use. It's up to you to ensure you have the rights to publish the work in question. And if you're selling the book in our Global Distribution network, that also means you must ensure you have the global rights to publish the work as it will be made available worldwide. In some cases, we may require you to submit proof that you have the right to globally sell a particular book.
Beyond that, if you wish to publish a large number of only public domain titles then Blurb may not be the best fit for you. Blurb is intended to be a platform for creative expression and original works. We may reject public domain titles that are too similar to existing versions of the same title available via other retail sites. We reserve the right to limit the number of Blurb-provided ISBNs that you may use. We may also limit the number of titles you upload to our distribution channels.