Digital Signature v. 6.4 -> 7.2.6 e 7.3.2 - Firma Digitale

I need support about digital signature in a writer file between version 6.4 and 7.2.6 and 7.3.2! Both of actual versions doesn’t support the 6.4 version!
I have a file with digital signature which was created with 6.4.! In 7.2.6 and 7.3.2 I don’t find it!
Is it compatible?
Thanks

Avrei bisogno di supporto per la firma digitale creata in un file di writer v. 6.4 e non visibile in 7.2.6 e 7.3.2 che sono le versioni attuali!
Sono compatibili?