I need to remind the user about copyright laws. If his books are still under copyright, downloading them for free without permission is illegal. My response must not encourage piracy. Instead, suggest legal alternatives like purchasing from legitimate retailers, using public libraries, or checking if the books are available in public domain.
I need to consider legal sources. Are his books available on platforms like Amazon Kindle, Google Play Books, or Kobo? Those might offer EPUB or PDF downloads. Also, maybe some Serbian or Eastern European sites host his works digitally. There's also the possibility that some books are in the public domain, but if they were published after 1926, they probably aren't.
I should also check if there are Serbian publishing houses that have digitized his books. Maybe the user is trying to find rare or out-of-print works. They might not be aware of the legal restrictions, so it's important to guide them towards proper channels.
Are there any Serbian digital libraries or academic resources? The National Library of Serbia might have digitized some books. Additionally, sites like Internet Archive sometimes preserve books, but I need to verify if they have legal access.
Another angle is using library databases or services like OverDrive or Hoopla, which can let users download e-books if they have a library card. The user might not know about these options. Also, Project Gutenberg and similar sites might have his works translated into other languages, but that's a stretch if they're modern works.
The user wants PDFs and EPUBs, so they're probably looking for a way to legally access his books. I should check if his works are available in Serbian or other languages. Maybe some of his books are translated, but the user might need to download them. But I have to be careful here because promoting piracy sites or enabling illegal downloads is against policy.