supports
Reports whether this provider supports appending to output file as opposed to always rewriting it. If this returns false, only WriteMode.REWRITE_FILE will be used and the PDF file will always be fully rewritten on save.
Note that if true is returned here, both WriteMode options must be supported by this DataProvider since some documents cannot be saved incrementally.
Return
true if this provider supports WriteMode.APPEND_TO_FILE save mode.