Invisible signatures by incremental update doesn't work at first sign ?

Hi all !

Sorry if here is not the proper place for my question. If it is the case, can anyone inform the right place ?

Well, I'm trying to build a tool to sign PDFs by incremental update using Delphi [] .

I'm newbie in PDF structure and short deadline made me desperate and maybe a little inattentive.

After 2 months of hard fighting I managed to get the Acrobat Reader know that my PDF (originally created by a java tool called SignServer) has a signature and recognize the certificate but it says that the certification is invalid because "the byte range is invalid".

I analysed the PDF in a hex editor and the signature byte range as well any other object offsets appears correct.

My test PDF is here: https://drive.google.com/open?id=0B0KKmaB-a0Z4SDZfNXdZRWZEem8

Can anyone to indicate me what is wrong with that PDF ?

Thanks a lot for any help !