Is there any java library for converting document from pdf to html?

Question

Open source implementation will be preferred.

Answer 1

Only ones I know of have to be paid for.

BFO
JPedal

Answer 2

Obviously, it isn't an easy task, PDF formatting is much richer than HTML's one (plus you must extract images and link them, etc.).
Simple text extraction is much simpler (although not trivial...).
I see in the sidebar of your question a similar question: Converting PDF to HTML with Python which points to a library (poppler, which is apparently written in C++, perhaps can be accessed with JNI/JNA) and to a related question which offers even more answers.