We have a pdf to pdfa conversion set in our environment.With certain pdfs the resulting file after conversion is a blank i.e.with no content.Certain characteristics that I noticed for the native pdf file are:-

1)It has a watermark.

2)One of the attributes that I see in the PDF-->Properties is that the PDF is secured.But the pdf is not password protected.

3)The pdf has been generated by a third party system.

Any help/pointers will be appreciated.