Yes. You need the latest released reader version in Linux, which I think was 9.5.5. At least this is the one that I tried LTV with, and it worked. It is easy to check whether the Linux Reader that you have supports LTV. Right-click on a signature. If the drop-down list contains "Add Verification Information" command, then this Reader version supports LTV. Remember two things:
1. LTV support in Reader 9 was introduced in 9.1 and was rudimentary. It was improved in Reader X but Adobe stopped releasing Reader on Linux after some 9.x version.
2. Make sure that you validate the signature at a time other than "Current". Reader does not use LTV when it validates a signature at the current time.
Thank you for your reply, but I'm having doubts.
When I right-click on a signature, in Adobe Reader 9.5.5 I don't get the "Add Verification Information" option.
I also don't understand, about the meaning of "Validate the signature at a time other than Current". Do you mean that the document must have a Timestamp?
I do not know what to say. On my Linux box with Reader 9.5.5 I do get "Add Verification Information".
Verification time selection is in Preferences->Security->Advanced Preferences->Verification->Verification Time choices. I believe that before 9.1 the default was "The current time", and after 9.1 it got changed to the "The time when signature was created". 9.1 was also version when LTV was introduced. That was for Mac and Windows. I do not know how Linux versions correspond to the Mac and Linux versions functionality-wise.