Yes. There is a Java interface that allows you to implement in memory handling of all output.
This is achieved by passing in your own implementation of CustomIO to the PDFtoHTML5Converter class. Details at http://files.idrsolutions.com/maven/site/jpdf2html5/apidocs/org/jpedal/examples/html/PDFtoHTML5Converter.html#setCustomIO-org.jpedal.render.output.io.CustomIO-
We also make available the existing code which handles this on which you can base your own implementation. Code at http://files.idrsolutions.com/htmlSrc/org/jpedal/render/output/io/DefaultIO.java.html